Windows has a lot of built-in tools that help you fix tons of system-related issues. One of them is the System File Check which is the tool you can use to conveniently replace potentially corrupted or missing system files with good ones. But what happens when it does not work? Well, you’ve come to the right place as in this post, you will be guided on how you can replace a corrupted single Windows system file manually with a known good copy of the file if the System File Checker scan is not working.
When you encounter this issue with the System File Checker, it will be unable to replace the corrupted system files and returns an error message instead. And so to fix and replace corrupted system files in your Windows 10 computer without the help of System File Checker, you can refer to the instructions provided below.
Step 1: First, you need to open the log files listed below and identify which particular file has been corrupted:
- %userprofile%Desktopsfcdetails.txt
- Log %WinDir%LogsCBSCBS.log
Step 2: You will see all the details on the given log files. Once you find out the name and the path of the file, you have to take ownership of this corrupted system file.
Step 3: To take ownership of the corrupted file, you need to pull up Command Prompt by tapping Win + R keys on your keyboard and then type “cmd” and tap Enter.
Step 4: After opening Command Prompt, type and enter the command below to execute it:
takeown /f FileNameAndPath
Note: In the given command, “FileNameAndPath” represents the name and the path of the corrupted file. For instance, the corrupted file is named “wuapi.dll”, then you need to type “takeown /f C:/Windows/System32/wuapi.dll”
Step 5: Next, you need to grant administrators full access & control to the corrupted file and you can do that via Command Prompt again.
Step 6: In the elevated Command Prompt, type and enter the following command to execute it:
icacls FileNameAndPath /GRANT ADMINISTRATORS:F
Note: We’re going to use the wuapi.dll again as an example. So the command should be like this: icacls “C:/Windows/System32/wuapi.dll /grant administrators: F”.
Step 7: Now all that’s left to do is replace the corrupted system file with a good copy from a trusted source. Once you have a copy, open an elevated Command Prompt again and execute the following command:
copy NewFileLocation FileNameAndPath
Note: In the command given above, the “NewFileLocation” is the location where you have saved the copy of the file. For instance, if you’ve saved it on your desktop, this is how it should look: “copy C:/Users/<username>/Desktop/wuapi.dll C:/windows/system32/wuapi.dll”
As in most usual online scams, everything starts with a strange email containing threats and other poorly written and composed speech. At the end of the given email, there would be a link claiming that you, of course, need to read it and follow instructions about the threat, if you click the link it will open a web page where you will have an innocent-looking PDF file with more information about the threat itself.
If you click on a seemingly innocent PDF file it will summon Windows 10's AppInstaller.exe tool, kickstarting a download-and-run process that'll put you in a bad place very quickly. From there, you'll have to deal with the dangers of malware BazarBackdoor, including data and credential theft.
This kind of scam is nothing new but the interesting thing here is that it uses App installer and by clicking on a link you are opening and giving permission for a malicious crook to use it. So, stay safe and do not click on any links from unknown emails no matter what. 
Before we move on to the discussion of fixing the underlying causes for error 103, it is important to understand all those programs that are most likely to generate this error. A list of all such programs is outlined below as follows.
