[Tarek]

I was copying 80G drive to an empty 80G drive by mistake I copied the empty drive to the one that contains data ... how can I solve this problem ??

[Alex]

Depending on the version you were using, either the entire disk is overwritten or only portions are overwritten. If the empty drive was partitioned and had a file system (albeit empty) on it, it's the best scenario, as almost nothing was overwritten. With normal recovery software you should be able to get a large portion of the original files back. Check for "Recuva", which is free.

If the disk was completely empty, then you're out of luck, as the entire disk is overwritten, and there's no known way of recovering the overwritten data.

If the disk contained some data, when using the Free or Basic edition, also the entire disk is overwritten. With the standard edition or the professional edition, only parts are overwritten (only those parts that contained data), but in this case it's still very difficult for a recovery software to gather information, as there is a completely valid file system (the copied one), and here and there are portions of the old file system shining through.