Do you have in your c:\windows\system32 folder the file called:
autochk.exe
If yes, rename the file to something you can remember like:
autochk.bak
Then you should magically see a fresh copy of autochk.exe appear in the c:\windows\system32 folder, but check the Event Viewer system log to make sure WFP did what it is supposed to do. You may not even be fast enough to see the replacement file go in, but if you watch, you will see it.
Since autochk.exe is one of the 3498 files that XP considers important, Windows File Protection (if it is working) will quickly and silently replace the now missing autochk.exe file with a copy and put a message like this in the Event Viewer System log:
Event Type: Information
Event Source: Windows File Protection
Event Category: None
Event ID: 64002
Description:
File replacement was attempted on the protected system file c:\windows\system32\autochk.exe. This file was restored to the original version to maintain system stability. The file version of the system file is 5.1.2600.5512.
To see the Event Viewer logs, click Start, Settings, Control Panel, Administrative Tools, Event Viewer.
A shortcut to Event Viewer is to click Start, Run and in the box enter:
%SystemRoot%\system32\eventvwr.msc /s
Click OK to launch the Event Viewer at recent events in the System log for a similar message.