C drive almost full but size of files does not match

I am running parallels build 5584 on a Macbook Pro Core Duo (not a core 2 duo) 15" laptop with 2G RAM and 160G HD.

I have 24.4G set for the C drive of my VM WIN XP OS. When I display the directory in the WIN XP it indicates that the C drive has used space of 22.7G with only 1.67G free.

However, if you add up the size of all the folders and files contained in the C DRIVE the total used is closer to 11G. I haven't been able to identify what has used up the additional 11G. I suspect somehow that the WIN XP registry has been corrupted.

I have checked for hidden files, I have run adaware and McAfee's anti-virus against it and have found nothing unusual. I didn't actually expect to find any virus or worm.

I did also run Norton Systemworks 2005 against the drive and it found some registry items to clean up.

I think what has happened as it seems it always seems to happen with WIN XP SP2 is that at some point I have to reinstall the WIN XP SP2 OS.

My question is: Should I try and reinstall parallels first or only run the WIN XP repair process? Has anyone else experienced this?

 

For what it is worth I ended up performing a repair re-installation of WIN XP and that seems to have corrected the problem. ( note: did not use the repair recovery option. I booted from the CD and selected the normal install route then when the CD detected the old OS I selected the repair option). Now I am waiting for the 89 security updates to be re-installed. Thank goodness for OS X. If I didn't have to use MS Visio I might never use WIN XP.