Corrupt XP dlls

I apologize for cross-posting this, but my query in the spyware forum seems to be a non-event. Although the problem was initiated by a virus, the real question is how do I replace corrupted operating system files without completely reinstalling the O/S. I guess that makes it somewhat appropriate for this forum.

I was infected with the Startpage.AY virus. It was detected and repaired by AVG Free. My computer continues to start very slowly and whenever I run AVG it shows the following files with the status 'CHANGED'.

c:/windows/system32/kernel32.dll
wsock32.dll
user32.dll
shell32.dll
ntoskrnl.exe

I assume these files were modified by the virus and AVG is unable to repair them. How do I clean them? System restore is off. My copy of XP is up to date with all patches, SP2, etc. I cannot reinstall SP2 because Windows update thinks its already installed. Can I obtain a clean copy of these files somewhere or do I have to completely reinstall XP?

 

I'd attempt a repair installation of XP.

 

Maybe try running SFC from Start-->Run. Type in SFC and press <enter>. You will need a M$ CD of your operating system to carry this out in full. SFC (System File Checker) may find that these files are corrupt and ask you to replace them. It may, of course, not find them as corrupt.

Another idea would be to obtain copies of these files from someone with a copy of the same XP OS. Rename the old files as oldxxxxx.xxxx where xxxxx.xxxx is the name of the corrupt file. Make sure the copy of the new file is placed in the same directory/folder, as the corrupt.one. REboot and see what happens.

I cannot guarantee what will happen, if you do this. In theory it should work, unless those files have varied from the original install. In any case, always backup your valuable data before stuffing around with this suggestion
All help given, but no responsibilty. Bazza