Fire up Task Manager (Ctrl-alt-del, Task Manager) and in the menu options there should be a setting to customize what is viewed. In that menu, select IO Writes and/or IO Reads. Go back to TaskManager, and you should be able to see which processes are accessing the disk... hopefully that should help you narrow it down.
Sorry for the vague answer, I don't have Win2K in front of me ATM... 🙂
Dave