Difference between folder size reported by Windows and total file size for Documents and Settings folder

"Almost unbelieveable that you 7.6 gb unaccounted for. I could see being off by a bit due to rounding off or hidden files.

First i would check my math, if correct you could try WinDirStat -it's an awesome little tool that doesn't need to be installed with a very nice GUI that may help you find something you missed.

Also, empty your recycle bin - i don't think that will account for the difference but it might. In your tags you have temporary files listed -if you believe that may be your problem i can recommend CCleaner. Would suggest the standard virus/malware scans also."