As Windows starts an error appears saying: ‘The application has failed to start because MFC71U.DLL was not found. Reinstalling the application may fix this problem’. How can I stop this message from appearing? The computer is running Windows XP Service Pack 2.

The MFC71U.DLL file is not specific to a particular program but is a shared library file provided by Microsoft which many different programs can use. We first need to check whether this file is missing from your computer or whether it is present (and may have just become corrupted). Since this is a DLL file which lives in the Windows System directory, you will first need to enable the viewing of hidden files and folders and we will also need to enable the display of file extensions (.DLL). Open My Computer or Windows Explorer and go to the ‘Tools’ menu > ‘Folder Options’. In the window that appears, click the ‘View’ tab. Enable ‘Show hidden files and folders’ and untick ‘Hide extensions for known file types’ then click OK. Then, navigate to the C:WindowsSystem32 directory. Look through the list of files for MFC71U.DLL. If this file is not present, it seems to be completely missing from your computer. On the other hand, if the file is present it may have become corrupted. In this case, rename the file to something else (e.g. MFC71U.OLD).

In either case, you now will not have a MFC71U.DLL file on your computer because either it does not exist, or you have just renamed the file to something else. So, we can extract a new copy of this file from the original Windows CD. To do this, we can use the Windows System File Checker utility, which will automatically scan for missing Windows system files and extract a fresh copy. Go to the ‘Start’ menu > ‘Run’ and type ’sfc /scannow’ (without the quotes) and click OK. The Windows System File Checker should now run. Once it has finished it will exit silently without any user feedback. At this stage, go back into the C:WindowsSystem32 directory and you should see a new copy of the MFC71U.DLL. If not, your next best option may be copying this file from another Windows XP computer onto your computer. However, if you decide to use this procedure make sure you observe any relevant copyright restrictions on the file.

If all else fails and putting a new copy of the MFC71U.DLL file on your computer does not resolve the issue, you could always just stop the application causing the error from loading on startup. It doesn’t seem to be loading at the moment, since the MFC71U.DLL file is missing, so assuming you are not currently having any negative side-effects you should not notice any difference. Should you wish to proceed, you will first need to determine which program is causing the error. You should be able to find the program/process name in the title bar of the window which displays the error. Once you have identified the program, go to the ‘Start’ menu > ‘Run’ and type ‘msconfig’ (without the quotes) and click OK. In the window that appears, click the ‘Startup’ tab. Here you will see a list of all processes which load on startup. Find the entry for the program causing the error and untick the entry. This will stop the process from loading on startup. Click the OK button and restart the computer. The error should no longer occur.