Disk Cleanup goes into a loop

I have tried to run Disk Cleanup (cleanmgr.exe) in Windows 2000 several times over the past few months. It seems to start off OK, showing that it's calculating how much space I can save, and is in the "Compress Old Files" stage of that process. The drive clicks away, and eventually stops... and cleanmgr.exe is taking up about 98% of the CPU. When I click the Cancel button, the window disappears, but Task Manager says it's still running and still eating CPU. I have another Win2K system, and it runs OK there.

I have exhausted every other avenue I can think of, including the Microsoft Knowledgebase, Google Searches and newsgroup searches. This is my last resort!