What is the exact message you get from the popup?
It sounds like the low disk space warning which then automatically takes you to the cleanup utility. If that is the case then try this:
http://pcsupport.about.com/od/windowsvista/ht/dislowdisk.htmMake sure to backup your registry first.
When you get the pop up that takes you to the cleanup utility are you logged in as Administrator. If not try logging in as Admin and manually run the cleanup utility on the D: drive.
If you do get access to your D: drive be careful what you delete as this likely contains your restore files from your computer maker.
