Windows 7 - 8GB disappearance each partition in win 7

I got one hardisk (Seagate SATA 7200rpm 80GB) on my windows 7 PC and I have had it partitioned into two partitions:
System C: 29.2GB
Logical D: 45.2GB

at the properties window I've come across by right-clicking the drive icon and click 'properties' it is said that the 'used space' in
C: is 26.2GB and in
D: is 33.2GB
as you can see at the 1st set of pictures.

but the thing is when I open C: or D: and blocked all the files in there (include hidden files and protected operating system files) and right-clicked on all the blocked files and clicked properties, the volume of those blocked files is 8GB SMALLER than the volume said in previous 'properties' window. see 2nd set of pictures please.

so where the hell is my 16GB? 8GB each partition. or is it normal?

well, little less than 16GB actually.
any clue?

You will find that certain directories (System Volume Information for 1) will not show any space being used. This 1 directory houses all your restore points so can use up quite a bit of space.

As this space is not being calculated by right clicking, it will not show as used space (as shown in your last 2 pics).

Hope this helps

I turned off system restore on D a long ago, is it safe to delete System Volume Information in D now?

You will need to do some vigorous security changes to get access to that directory but i think it should be ok.

Also, click the scales icon to add/minus rep to people

Add: if you hover the mouse over each icon you get a description of each

okay I get it, thanks, but I can't get that System Volume Information deleted.

It is a real pain in the a$$ to say the least. You could try following the takie ownership tutorial here Take Ownership Shortcut and see if you can delete the folder afterwards.

I already has that take ownership context menu, I take its ownership and see a command prompt scrolling about 5 seconds. but still, I cant delete it. I delete it, I click yes, but it's still there and my partition don't free up.

I've had the same think happen to me. In this pic my external HD was freshly formatted this morning and after restarting you can clearly see the directory there. It might be that it is indeed empty but i, like you, can't get rid of it.

If that's the case then there must be some underlying directories & files that are causing incorrect size info but i don't know how to tell

really? is it happen only on windows 7? thanks for the info anyway, another rep for u.