>Many thanks for you Hilmar,
>
>This was helpfull, let me tell you the problem, we use the D: partition 80GB to store our developed system image files (abour 150000 file),in addition to that we store more applications.
>
>When I display the D: partition propirites it shows the used capacity about 50GB, but when I select manualy all the folders in the same drive D:, and right click the mouse then select propirities it show the total number of files and show the used capacity about 35GB!!!
>
>So, where is the problem? do I have to compress the drive or something else is wrong?

The answer is quite simple (I believe): cluster size. A file takes up one or more clusters, of 1/2, 1, 2 or 4 KB each. Let's assume, for the sake of the discussion, that your cluster size is 4 KB.

A 1 KB file (or less!) will take up one cluster (4 KB). The remaining 3 KB are not available for other files - although Windows NT might have a few additional tricks which I don't know in detail.

Similarly, a 5 KB file won't fit into a single cluster, so two clusters are used (that is, 8 KB).

The problem here is that you have many small files. A few large files generate much less waste.

Your options include:

Reduce the cluster size.

Save your data in a few large files, instead of many small files.

Compression would probably help, too.

HTH, Hilmar.

Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)