... and on top of that all, how big is your Recycle Bin size from the HD size? Did you uninstall the game (probably not) or just delete it (probably yes)? If you just deleted, check in your Recycle Bin and see the size of it, there's a chance that all the stuff you deleted actually ends up there. Of course, this always depends on the size assigned to the bin and the HD size, but if it's a big HD (say 10+ gigs) and the bin size is some 10% of HD size (what the stupid default settings at times set it to), then it can be very well in the bin.

Also check your C:\TEMP folder and remove the trash in there; check C:\WINDOWS\TEMP and remove the trash from there (make sure you always empty the Recycle Bin from the trash as well).

Press "Start" - Find - Files or Folders.. and search for "Baldur" or "Black Isle" and delete these folders. Run the "Add/Remove Programs" in the Control Panel and check what stuff you all have installed in the first place. People keep installing one little thing and then another, thinking that 1 little thing never hurt anyone. True, but 100 little things sure do hurt.

Run Scandisk and let it check for the crappy stuff. That usually happens when you shut down your PC in 'abnormal' way, i.e. cut the power off; press hardware reset button since something hang the PC big time; had a power loss in the house while PC was running.. Run Defrag and let it finish. Check the size of the swap file. Really, many things here. Check these out and see if it helps.