[TimCraig]

I've had the happen to several of my computers although your mileage may vary. There's a program that XP starts named ciscv.exe which monitors the program that does disk indexing to keep it from going wild. The only problem is that ciscv.exe sometimes goes off its nut and takes over. Open MyComputer and right click on the hard disks to bring up their properties, if the check box at the bottom "Allow Disk Indexing..." isn't checked, this isn't your problem. If it is, you can try unchecking it and pressing apply. Do it for all directories and files. This may take a few minutes.

Another way is to open the task manager and kill cisvc.exe and see if your computer acts more normally. If it does, then do the above. No harm since Windows will restart it next boot if this isn't your cause.

If you want to really verify this, use the filemon program from SysInternals.com mention in one of the other posts.

It's interesting that Microsoft is using one program to make sure another doesn't misbehave and that program them misbehaves.