You can use Restoration to get back files you deleted, it will also wipe your HD clean of all files you've deleted.

I don't delete files anymore, if I want something deleted it's because I know I don't want it. I use Eraser instead. It wipes the HD(can't get files back) clean. You can try that to wipe your vacant clusters.

Both programs are free, read the instruction well !, sure don't want your HD to disappear