sfc_os.dll found on windows xp

Hello everyone,
In recent days, some computers in my domain are giving me the following error at startup and "freezes" in the future. I am Unable to "log" or do anything on the computer.

"Winlogon.exe"
"This application has failed to start because sfc_os.dll is found. Reinstalling the application may fix this problem."

- Unable to log windows in normal mode or in Safe Mode
- Sfc_os.dll is already present in c: \ windows \ system32 \
- They are all on windows XP service pack 2

After several searches, I tried some solutions but nothing seems to work long term.

First, replaced sfc_os.dll in c: \ windows \ system32 \
-> Does not work

Second, choose "last good configuration" at startup of windows.
-> Only works for about 1 or 2 days ...

The only way to solve the problem seems to reinstall Windows. (I use RIS (Remote Installation / Windows Deployment Service) + GPO)

My question is:

- Is it a file other than sfc_os.dll which is causing this problem?
- What are the causes of this problem?
- Is this a virus?

Thank you for your help!

Do a Windows repair:

Sometimes the system files (those required to run Windows properly) can become corrupted. Here's how to run a check on your system files:
• Click Start; Run.
• In the Run box, type cmd.exe to open the command prompt window.
• At the prompt, type sfc.exe /scannow
• Press ENTER. If Windows finds problems with the system files, you will be prompted to insert your Windows XP installation CD to restore the files.

If no problems are found and the scan finishes, type exit and press ENTER.

hi, I have been looking for lots of solutions on WFP, most of the solutions require you to hack the sfc_os.dll or sfcfiles.dll, and this requires a lot of effort.

And I have tried many times, even downloaded the hacked sfcfile.dl_ and replaced it in the source CD, but this still didnt work.

SFC_OS.DLL is a service-pack file, so you should be able to restore it from the SP1 CD (I've got that file, and I don't use SP2 so it must be from SP1). The file belongs in C:\Windows\system32
and also in C:\Windows\ServicePackFiles\i386

Both files identical, dated 29/08/2002, 130Kb in size.