Obviously, something appears to be running outside of Windows XP Pro SP.3. Unfortunately, I am unable to find and DESTROY it.
One thing I can tell you is, it’s not outside of Windows. Your assumption that CPU usage is telling you something is incorrect.
In the past, I’ve recommended a tool called FileMon to determine what’s been writing to your disk. FileMon has been replaced by a significantly more powerful utility, Process Monitor.
We’ll look at using Process Monitor to see if we can determine just exactly who’s doing what to your machine.