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Check Windows 10 system files with System File Checker

Updated July 20, 2020

I was thinking the other day about what program I use the most in doing computer repair. The one program I use the most on Windows computers would have to be System File Checker (SFC). SFC checks for system files that may have gotten corrupt or replaced with incorrect versions. Here's how to check Windows 10 system files with System File Checker.

Check Windows 10 system files with System File Checker

SFC has been included in every version of Windows since Windows XP. You can also build it into the Microsoft Diagnostics and Recovery Toolset (DaRT). There is no shortcut or link to SFC in Windows 10, as it runs inside an Administrative Command Prompt.

How to open a Command Prompt with Administrator privileges in Windows 10

SFC running inside of Windows 10 Administrative Command Prompt

The following is the syntax and switches for SFC. The most commonly used syntax/switch is: sfc /scannow.

SFC [/SCANNOW] [/VERIFYONLY] [/SCANFILE=<file>] [/VERIFYFILE=<file>] [/OFFWINDIR=<offline windows directory> /OFFBOOTDIR=<offline boot directory>]

/SCANNOW (Scans integrity of all protected system files and repairs files with problems when possible.)
/VERIFYONLY (Scans integrity of all protected system files. No repair operation is performed.)
/SCANFILE (Scans integrity of the referenced file, repairs file if problems are identified. Specify full path <file>.)
/VERIFYFILE (Verifies the file's intergrity with full path <file>. No repair operation is performed.)
/OFFBOOTDIR (For offline repair specify the location of the offline boot directory.)
/OFFWINDIR (For offline repair specify the location of the offline windows directory.)


sfc /scannow sfc /verifyfile=c:\windows\filetobereplaced.dll sfc /scanfile=d:\windows\filetobereplaced.dll /offbootdir=d:\ /offwindir=d:\windows sfc /verifyonly

Once SFC is done scanning the system files, it will give one of four possible results:

  • Windows Resource Protection did not find any integrity violations.
    All system files are fine, and you're good to go.
  • Windows Resource Protection could not perform the requested operation.
    There may be another program preventing SFC from running. In this case, boot the system up into safe mode and run SFC from there.
  • Windows Resource Protection found corrupt files and successfully repaired them.
    All system files are now correct, and you're ready to go. If you want to view the repair details, see below.
  • Windows Resource Protection found corrupt files but was unable to fix some of them.
    If you get this message, SFC found a file or files that it couldn't repair. The next thing you will need to do is find out the name of the file(s). Using the Find String utility, you can filter out the SFC results with only the scanned components and create a text file with that information on your Desktop called sfcdetails.txt. Just copy the following code into an Administrative Command Prompt:

findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log >"%userprofile%\Desktop\sfcdetails.txt"

Manually replacing a corrupt system file in Windows 10

Note: To replace a corrupt system file, you will need to have a known good copy of the file(s) in question. A good source for files is another computer or virtual machine running Windows 10. Since I do computer repair for a living, I have all of the versions of Windows that are still supported by Microsoft running inside of Oracle VirtualBoxes.

The first thing to do is note the location (path) and name of the file(s) that need to be replaced from the sfcdetails.txt file. Once you have another copy of the corrupt file(s), you will need to take administrative ownership of the file(s). To do this, modify the following command with the path\filename of the file you want to replace and then type it into an Administrative Command Prompt:

takeown /f path\filename

Example: takeown /f C:\Windows\FileToBeReplaced.dll

Next, you will have to grant administrators full access to the file(s) being replaced. To do this, modify the following command with the path\filename of the file you want to replace and then type it into an Administrative Command Prompt:

icacls path\filename /grant administrators:F

Example: icacls C:\Windows\FileToBeReplaced.dll /grant administrators:F

The third thing to do is copy over the new file(s) and replace the corrupt one(s).To do this, modify the following command with the path\filename of the file you want to replace and then type it into an Administrative Command Prompt:

copy path\filename path\filename

Example: copy C:\Temp\FileToBeReplaced.dll C:\Windows\FileToBeReplaced.dll

Maintain your hard drive with SpinRite

When it comes to maintaining a hard drive, running a disk check will usually find any software-related issues. But when I need to check the hardware inside a hard drive, I will use SpinRite from Gibson Research Corporation.

Intro screen from GRC SpinRite
Intro screen from GRC SpinRite

SpinRite is a magnetic storage data recovery, repair, and maintenance program and works only on HDDs (Hard Disk Drive) and not SSD's (Solid State Drive). SpinRite includes a feature called DynaStat that can reassemble missing data from bad sectors. SpinRite is a self-contained program that runs on top of a version of FreeDOS (Free Disk Operating System).

Graphic Status Display screen from GRC SpinRite
Graphic Status Display screen from GRC SpinRite

SpinRite has five (5) levels of operation, each building on the previous level.

  1. Examine the hard drive surface. This level will read every sector of the selected partition(s) psychical surface looking for areas that appear to be healthily but could fail in the future.
  2. Recover unreadable data on the drive. This level will read every sector of the selected partition(s) psychical surface looking for unreadable data. Spinrite will then attempt to recover unreadable partition data using the built-in advanced recovery technology.
  3. Refresh the hard drive surface. This level will read and write every sector of the selected partition(s) psychical surface, mainly exercising the hard drive. It tests and verifies every sector on the partition(s).
  4. Locates surface defects. This level will read, write, and invert every sector twice of the selected partition(s) psychical surface. This tests and verifies that every 'bit' on the selected partition can be successfully written to and retrieved.
  5. Restore known good sectors. This level does everything that all of the other levels do and restores any areas that may have been previously marked as defective, but now are reliable.

DynaStat Data Recovery screen from GRC SpinRite
DynaStat Data Recovery screen from GRC SpinRite

To run SpinRite, you will need to create a bootable media, either a CD or USB drive. Typically, if your computer runs Windows XP, Windows Vista, or Windows 7, all you have to do is insert the bootable media and restart your computer. If your computer doesn't boot up to the SpinRite media, you may have to change the boot order in the system BIOS (Basic Input/Output System).

If your computer has Windows 8, Windows 8.1 or Windows 10, more than likely your computer has UEFI (Unified Extensible Firmware Interface) enabled BIOS. To run Spinrite on one of these systems, you defiantly have to go into the BIOS and turn off the UEFI boot functions temporality.

Now, suppose in either scenario, SpinRite doesn't recognize your hard drive. In that case, you may have to also change the drive mode in the BIOS from AHCI (Advanced Host Controller Interface) to ATA (AT Attachment) temporarily.

SpinRite is available from Gibson Research Corporation for $89 (as of this writing). For more information on SpinRite, follow the link below.

Gibson Research Corporation SpinRite

How to replace a CD/DVD/BD drive in your desktop computer

When it comes to desktop computer repair, one of the most common hardware failures is CD/DVD/BD drives. If you're having problems with getting the disk tray to eject or disks are not being recognized, it may be time to replace it. Here's how to replace a CD/DVD/BD drive in your desktop computer.

How to replace a CD/DVD/BD drive in your desktop computer

So you're tired of trying to get your old desktop CD/DVD/BD drive to work and are ready to replace it with a new one. Having to use a paper clip to manually eject your computer's CD/DVD/BD drive tray can get old quick. Replacing a desktop CD/DVD/BD drive is relatively easy; you have to make sure you get one with the correct connections and dimensions.

Find a new drive

The majority of CD/DVD/BD drives on the market nowadays will have SATA (Serial ATA) connectors for data and power. But there are still quite a few older systems that still use PATA (Parallel ATA) for data and 4 Pin Molex for power. SATA type drives are the de facto standard, so finding PATA replacement drives can be tricky. Newegg and TigerDirect are good places to find these older style drives.

SATA and PATA drive connections
PATA and SATA drive connections

Desktop CD/DVD drives have standard width and height dimensions, so all you have to do is check your existing drive's depth. Sometimes you have room to put a deeper drive in, and sometimes you don't. Always check to see what kind of space you have available before purchasing a replacement drive.

Uninstall the old software

Once you have your new CD/DVD/BD drive, you will need to uninstall the software that came with your old CD/DVD/BD drive. It's usually a version of Nero or PowerDVD, and it is branded to your old drive. Once you remove the old drive, the software that came bundled with it won't work anymore. Your new drive should have come with its own disk burning software.

Install the new drive

From here, we need to turn the computer off, disconnect the power cord from the back of the system, and open up the case. Now there are two possible ways of mounting the CD/DVD/BD drive in the case: screws or quick release rails. You may have to remove the front bezel from the case to access the CD/DVD/BD drive, as it will need to come out the front of the case. Please note the connections and remove the old drive and replace it with the new one.

Drives attached by screws and quick release rails
Drives attached by screws and quick release rails

Install the new software

Once you get the system back together, power it up, and let Windows discover the new CD/DVD/BD drive. Windows may require a restart to finalize the setup. After that, you are ready to install the software that came with the new drive.

The most common computer video display connectors

When it comes to computer repair, you have to be prepared to work on different types of systems. One of the biggest issues is having the correct video display connector. With more than ten different types of connectors it can be difficult to identify the correct one. Here is a list of the most common video display connectors.

What type of video connector do you have?

Most common video display connectors  
3 variations - 4, 7 or 9 pins.
S-Video display connector
VGA (Video Graphics Array)
2 variations - DE-9 (9-pin) & DE-15 (15-pin).
VGA display connector
DMS-59 (Dual Monitor Solution, 59 pins)
It provides two DVI or VGA outputs in a single connector. An adapter cable is needed for conversion from DMS-59 (digital) to DVI (digital) or VGA (analog).
DMS-59 display connector
DVI (Digital Visual Interface)
5 variations - DVI-I (Single Link), DVI-I (Dual Link), DVI-D (Single Link), DVI-D (Dual Link) & DVI-A .
  • DVI-I (integrated, combines digital and analog in the same connector; digital may be single or dual link).
  • DVI-D (digital only, single link or dual link).
  • DVI-A (analog only).
DVI display connector
HDMI (High-Definition Multimedia Interface)
Electrically compatible with the DVI.
4 variations - Standard, Dual-Link, Mini and Micro.
HDMI display connector
Backward compatible with VGA and DVI through the use of adapters.
3 variations - Standard, Mini and Micro.
DisplayPort display connector

My digital toolbox

Every computer repair technician has a digital toolbox, more than likely several. They are either on a CD / DVD or USB drive and contain programs that we use regularly. Here are a few of the programs that I have in my digital toolbox.

My Digital Toolbox

All of the following programs have one thing in common; they don't require installation. Just right-click on them in File Explorer and select Run as administrator, that's it. Some of the programs may require access to the Internet for complete functionality.


AdwCleaner is one of the best stand-alone adware removal tools I have found yet. Right out of the box, and it will scan your system with a generic set of definitions. But if you are connected to the Internet before you start up AdwCleaner, it will download a current copy of adware definitions. And if you select uninstall, it will remove any quarantined files and then delete itself.


.NET Framework Cleanup Tool

When it comes to resolving .NET problems, you are sometimes better off just removing and reinstalling the framework. The .NET Framework Cleanup Tool is a stand-alone program that does just what its name implies. Just pick the version you wish to remove (or all) and click Cleanup Now. Once it is complete, reboot and use Windows Update to reinstall whatever version of .net framework you need.

.NET Framework Cleanup Tool

Sysinternals Suite

Sysinternals is hands down, the best collection of Windows troubleshooting tools. All of them are stand-alone programs, over 70 altogether from seeing everything that automatically starts up with Autoruns, exploring running processes with Process Explorer, or monitoring network usage with TCPView. When it comes to Windows diagnostics, you cannot beat the Sysinternals Suite.

Sysinternals Suite

Free computer diagnostics

Repairing a PC can sometimes be expensive, and that is why we offer free basic in-shop diagnostics. Give one of our professional and experienced technicians a call at (602) 795-1111, and let's see what we can do for you.

Check out our reviews

Geeks In Phoenix LLC, BBB Business Review

Customer service is #1

Here at Geeks in Phoenix, we take pride in providing excellent customer service. We aim to give the highest quality of service  from computer repair, virus removal, and data recovery.

Bring your computer to us and save

Repairing a computer can be time-consuming. That is why we base our in-shop service on the time we work on your computer, not the time it takes for your computer to work! From running memory checking software to scanning for viruses, these are processes that can take some time.

Contact us

If you have any questions, please feel free to give us a call at (602) 795-1111  and talk with one of our Geeks. Or you can send us a message from our contact page contact page , and one of our Geeks will get back to you as soon as possible. Or you can stop by and see us. Here are our hours and location.

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