Help! Hard Drive Space vanished in Win XP

My computer is running XP sp 2.

Size of the HDD is 50 GB, all files and folders added together (including hidden files) amount to about 20 GB. But windows is showing that I have only 5 GB of space left, having used a total of 45 GB. I have turned off system restore, etc, but this still doesn't make up for the 25 GB of space that is mysteriously taken up. Scan disk didn't find any error. I ran SpaceMonger, it showed a 25 GB "unscannable" sector. A different program called Scanner showed that I have 28 GB of free space.

Please help me recover my lost HDD space.

 

This thread might help you find the files taking up the space.
http://forums.majorgeeks.com/showthread.php?t=145459