Hi Lanny, i have never used them so i haven't a clue how strong they are, i suppose it would depend on what size gigabyte hardrive were talking about too, if you go to the hardrive manufacturers support page and email that question to them, they MAY be able to tell you.

A very good tip that MrD told me was to put a piece of moleskin under the magnet to stop any magnetic burn, which has happened to me once, it leaves a very red unpleasant round mark on your skin which takes a few days to go.
If the magnets are only real small you don't need to do that , but if they are real powerfull it would be wise to put the moleskin underneath the magnet.

Just remember that opposite poles attract to each other, if you are placing anymore than one magnet in one area, place them down on a flat table whilst holding them firmly very slowly move them towards each other, if they start to attract STOP and flip one of the magnets over to the otherside, if you try the same again, you will notice now that the magnets will push away from each other, now thats how you should place them on yourself,[pushing away from each other] this creates the magnetic field you want.
good luck
Brian