The motherboard on my computer failed and I had to put the hard disc from my old computer to a new one, but now none of my auto programs that I've purchased say that I've registered them.
Do I just need to re-register them using my paypal recipts/etc, or do I have to buy them all again?
They should still be registered. You need to make sure the new pc is wired to the old hard drive.
So it can't be a slave to the other HD?
If you hook it up correctly.
Actually I would make the old HD the master.