Another thing to keep in mind. Installing new software will increase the risk that your deleted files will be overwritten (the newly free space being used by the new software), so if you really want to get your files back, your best bet is to take out the hard drive, install the programs on a seperate PC and run them on that with the old hard drive plugged in with USB case for example.
Its a small chance that new software will overwrite JUST the part you need to restore, but its still a chance. And with a situation like this, you need all the luck you can get, so risking it wouldnt be ideal