I have something that I have no idea if it will work but it sure can't hurt anything. Use the built in Windows 7 Disk Cleanup.
From Help and Support.
If you want to reduce the number of unnecessary files on your hard disk to free up disk space and help your computer run faster, use Disk Cleanup. It removes temporary files, empties the Recycle Bin, and removes a variety of system files and other items that you no longer need. For more information about deleting files from the Recycle Bin, see Permanently delete files from the Recycle Bin.