What you need to do is create the boot CDs. Once that is done, run a program that will overwrite the partition/volume 3 to 5 times with various combinations of 1s and 0s. That's needed to change the residual magnetic field on the hard drive.
After something like that you would need some very expensive and specialise equipment to recover any data.
The quick format and deleting files, all it does it marks a file for deletion. All you need to do is run a program which scans the drive/filesystem and presto, you have your files back.
Running a full format still doesn't delete all the files and they can be recovered, but it destroys the current filesystem and writes a new one. So what is needed than is a program that can find what's called "magic numbers" and it will be able to recognise the files and copy them off to another drive.