I.E. 7 in connection with Disk Cleanup

I have a little glitch that recently showed up.
I go to Control Panel/Performance and Maintenance/Free up space on your hard disk. The Disk Cleanup box opens -- and then I get a pop up stating that Internet Explorer has encountered a problem and needs to close. I did not have Internet Explorer open.

The second part of the problem is that Disk Cleanup then shows me that I can free up around 940,300 kb of space for the items I have selected. The largest portion of this is under "Compress old files." So I click OK and I'm asked if I'm sure I want to do this and I click yes. It runs and appears to be working; however, when it's finished, I close it down, reopen it and discover that nothing has been removed. It still shows the same 940,300 kb.

Does anyone know why either of these things are happening?

Nikilet