Windows 7: HDD memory size lost

hi frens
i have attached the pic which makes everything clear. the total size and the free size of the hdd is shown when we open my computer . but when i explore that drive and select all the folders and files contained by that drive then totol sum of the free space and the used space is alwas less than the total size of the drive. for example my total size of c drive is 97.5GB and the total size of the folders and files shown in property is 15.9 GB and free space is 74.3GB . where did 6.4 Gb lost. please help me to get back the hidden space

Look here and download a disk space usage tool.
Best Free Disk Space Analyzer
Explorer can be deceptive.

Have you checked to see what the size of your System Restore folder is? Other things that take up space on the C partition are the page file and hyber file. Windows creates a page file equivalent to the amount of RAM you have installed, which in my case is 8 Gbs. With 8 Gbs of RAM I don't need a page file that size so I have reduced the size to 2 Gbs to save space. Also, since I don't use the hibernate feature, I turned off the hyber file to save more space.

thanks for the response . i have removed all restore poing by using cc cleaner and one is there which is undeletable but still the total sum is not matching the drive size. is it due to the last restore point? what is the size occupied by the restore point? thanks .

thanks for providing the software but i have purchased treesize and downloaded windirstat but the problem is the consumed size shown by these application so which one to believe and which not? it made me more confusing. for example is ,,the total size used in the c drive is different and also the size occupied by windows is also diffrent.....so plese help me out of this

Different tools calculate space differently, but the variation shouldn't be great.
It's possible one is reading hidden files and one isn't.
I didn't try to analyze your screen prints, because this type of space discrepancy is usually caused by hidden files. Besides, my eyes are tired
The files LittleJay mentioned are hidden unless options are set to show them.
See if your files are hidden by looking at this.
Show hidden files

First as LittleJay said, check your pagefile size.
To do it follow this :

Right-Click on Computer -> Properties -> Advanced System Settings -> (Performance) Settings -> Advanced Tab -> (Virtual Memory) Change.

On total files size add pagefile size for C and you will know how much is used.

Trinty

No, a single restore point won't take up that much space. How much RAM do you have installed? Have you checked the size of the page file using the instructions Trinity gave you? And like I mentioned before, if you have hibernate enabled, that will take up space as well. See the tutorial below on how to enable, or disable the hiberfile.

Hibernate - Enable or Disable

i have 4 Gb ram and one more question is the GB that it is showing is conversion of taking 1000MB =1GB like hard disk is purchased of 500 GB but it is just 465 GB . or is it calculated of 1024 basis?

i have 4 Gb ram and one more question is the GB that it is showing is conversion of taking 1000MB =1GB like hard disk is purchased of 500 GB but it is just 465 GB . or is it calculated of 1024 basis?