Well, that is a commono misunderstanding.
1. Your 500GB (decimal) capacity shows as 465GB (binary) in the system.
2. To get a true count of all the files run WinDirStat ( WinDirStat - Windows Directory Statistics
). Only than you will have a true count.
3. Finally, up to 15% of your OS partition is used for shadowstorage - and that you do not see in the above. For a better understanding I have made this write-up: With each install and uninstall, Vista writes a shadow (restore point) of about 1GB - plus one is written each day. For that purpose Vista reserves 15% of your OS disk partition and allocates/uses it as needed. Find Command Prompt (in All Programs > Accessories > Command Prompt), right click on it and Open as Administrator. Into the little black window type VSSADMIN LIST SHADOWSTORAGE and hit ENTER. It will show 3 numbers: Allocated - that is the amount that it has grabbed from your OS partition at this time Used - this is the amount currently used Maximum - this is the ultimate amount it will allocate and use Once you reach "maximum", it will reuse the space deleting the oldest shadows for the storage of the newest shadows. With e.g. an appr. 200Gb of OS partition you should expect a maximum of 30GBs that are reserved for the system and that you cannot use. If your OS partition is larger or smaller, the shadowstorage will be accordingly (always 15% max.) But the restore points (shadows) are required the day you need to do a system restore PS: If you need to reduce the amount of shadowstorage ( which I do not recommend), you find the procedure here: http://www.downloadsquad.com/2007/04...ystem-restore/