Missing HD space,its not the bin ;),plz help!!

Ok, I looked everywhere, but no answer came up. My problem is as follows:
After deleting data from hard drive, free disk space is still reported as being in use. That means, even after deleting files free disk space is not available. All together Im missing about 5 GB on my second partition D: (NOT the one where xp is installed). It happens only sometimes, usually by deleting files from 100-700 MB. If I mark all files on D:, all files together take less space than windows says they do by looking at the total free/used space tablet (of course I turned 'show hidden files and folders' option on).

I already tried the following:

-Empty recycle bin , greatly reducing it's storage size
-Disabeling hibernation/standby option
-Running chkdsk /f
-Disabeling Windows system recovery option
-Empty Norton protected files

I dont have a clue what else to do, please help me out here..