Disk Drive appearence problems. Help!

I am using windows XP media center edition. it worked fine in the first, and even now but the problem is about the disk space of the D: and E: drives.
here it goes, the disk space(used) of the drives appears more than that of the size of the files on the disk. i tried moving all the files to the other drive, even then the used disk space is 3GB(but the disk drive is empty). i tried formatting but an error message appears saying that the drive is in use, same even with other drive.
can anyone please help me. i'll be very thankful.

[murphyslaugh]

I'm not sure but windows might be configured to use that drive for paging. right click on my computer -> properties -> advanced -> performance options -> advanced -> Virtual Memory(Change). That'll give you an idea if its being used for that purpose or not

[techtronic]

What is the partition type
FAT 32 or NTFS ?

If its NTFS,check whether u have enabled compression under Advanced Options