Math not adding up (caviar green)

[madrox68]

as stated i have a newly purchased caviar green 1 tb

installed vista on it, clean install, and only well trusted other installs on the drive

on installing vista i noticed that it read the disk as only 931 gb's, which just seemed off to me

now while it still reads as 931 GB the issue here is this

30 seconds ago i clicked on my computer and it had 871 GB free, well then i went and opened the net and started dragon age and grabbed a bowl of cereal. i come back and reopen my computer to discover that it has suddenly dropped dow to 867 gb of free space and i didnt install anything,

so deciding WTF, i added up all the information in my computer roughly by opening c:\ and simply highlighting all folders and files at once and hitting properties which returns me a 40 gig number, while this may not be a accurate way to do things i somehow doubt i should be off by 20 gigs

not to mention its kinda humming, very lightly

ny idea's on whats going one here?

 

[madrox68]

so after playing dragon age for about oh 30 minutes its decreased to 866 gb

 

[sminlal]

First of all, drive manufacturers quote capacity in decimal: (1TB = 1,000,000,000,000 Bytes) while Microsoft shows them in binary (1GB = 1,073,741,824 bytes). So even if the disk was completely empty, Explorer would show only 931GB available (931GB in binary = 1TB in decimal).

Secondly, the OS itself, along with the page file, hibernate file, recycle bin and volume shadow copies all take up space. You can check the amount of space used in shadow copies by referring to this article: http://www.tomsguide.com/us/windows-vista-solutions,review-1179-2.html