Win File Protection

I've been a getting this pop up every 5-10min

Windows File Protection
Files that are required for Windows to run properly have been
replaced by unreconized versions. To main system stability
Windows must restore the original versionf of these files

Insert you WinXP Pro CD-ROM now
<retry> <more info> <cancel>

When I insert my WinXP CD it doesnt reconize it so now every so often when I'm in the middle of something this thing pops up. Its really annoying, I dont even know which files have been replaced or what did it. Anyways.. anyone else have this problem? Is there a way I can get rid of it?