Unless you are keeping secret documents on your personal computer what's the point?
You do a low-level format, and it actually changes each individual bit on the hard drive.. no more data.. and from there I don't think you can recover anything unless you spend BIG money to POSSIBLY detect the minute changes in the magnetic or electonic field(I really don't think that it is possible) on each bit that has been changed. The ones that have been caught in the past, are the ones that thought de-fraggin was the answer.. They would delete files, then de-frag their computer in hope of writing over the files they deleted, that does NOT work. Many a child porn afficianado's have been caught that way.
Magnets do not work either.. You see it in the movies, a house gets raided, and they swipe a huge, 20lb or so, magnet across their harddrives and their media.. doesn't work.. maybe against an older Floppy disk, but not against a Hard Drive.
Remember it's all ones and zeroes(electrical charge, NO electrical charge).. if you can erase all the ones, and make them all zeroes there is NOTHING there.