The System File Checker (SFC) tool is a powerful utility in Windows that allows users to scan and repair corrupted system files. “sfc /scannow” is a specific command you can execute in the Command Prompt to initiate this process. This guide will walk you through the steps to use this tool to repair your Windows installation.

Step 1: Run Command Prompt as Administrator

1. Press the Windows key, type cmd or Command Prompt in the search box.
2. In the search results, right-click on Command Prompt and select Run as administrator.

If a User Account Control (UAC) window pops up asking if you want to allow this app to make changes to your device, click Yes.

Step 2: Run the “sfc /scannow” Command

1. In the Command Prompt window, type sfc /scannow and press Enter.

Note: Make sure you include the space between “sfc” and “/scannow”.

2. The scan will begin, and it may take some time to complete (usually between 15 minutes to an hour, depending on your system and the extent of file corruption).

During the scan, you’ll see a message that says “Beginning system scan. This process will take some time.”

Step 3: Interpret the Results

Once the scan is complete, you’ll see one of the following messages:

1. “Windows Resource Protection did not find any integrity violations.” This message indicates that your system doesn’t have any missing or corrupted files.
2. “Windows Resource Protection found corrupt files and successfully repaired them.” This message shows that the SFC tool found corrupted files and fixed them. Details are included in a CBS.Log file.
3. “Windows Resource Protection found corrupt files but was unable to fix some (or all) of them.” In this case, the SFC tool found issues it couldn’t fix. The details of these issues are also recorded in the CBS.Log file.

Step 4: Access the CBS.Log File (Optional)

If SFC repaired files, or if it found corrupt files it couldn’t fix, you might want to view the details in the CBS.Log file. Here’s how:

1. In the Command Prompt window, type the following command and press Enter:
   
   findstr /c:”[SR]” %windir%\Logs\CBS\CBS.log >”%userprofile%\Desktop\sfcdetails.txt”
   
2. This command will create a new text file on your desktop called sfcdetails.txt containing the details of the scan.
3. Close the Command Prompt window.
4. Navigate to your desktop and double-click sfcdetails.txt to open the file and view the details of the SFC scan.

Remember, the “sfc /scannow” command is a helpful tool when trying to resolve issues related to corrupted or modified system files. However, it might not be able to fix all problems, especially those that are deeply rooted or complex. In such cases, you may need to perform a system restore or reset your PC to a previous state or even consider a clean installation of Windows.