Eremon1

It's difficult to say without looking, but if I had to guess I'd say that maybe its one of these things;

1.System Restore has more reserved than normal. To check this right-click on My Computer and select Properties. Then goto the System Restore tab.

2.Perhaps the Recycle Bin has a good chunk of the disk reserved, to check that right-click on the Recycle Bin and select properties. There you should see a slider that sets how much drive space is reserved for deleted files.

3.If it isn't those things I'd also check the windows swapfile size and see how big it's been set to. Right-click on My Computer and select Properties, then the Advanced tab. In the Performance box hit the Settings button and then Advanced tab. At the bottom there should be a box Virtual Memory with a button Change. Hit that and there you can see how big the Windows PageFile<Swapfile> is in MB.

Try that and report back your findings if you were successful or not.