You folks guessed right, my drives are not powered by external power. I'm really surprised that the PB 17" USB 2.0 ports don't have enough juice, isn't that weird?

I'm very optimistic, what I can try and do is use my old PB 12" which, in fact, these drives mounted on before. If that fails, I will have to get that IDE->SATA converter and try it that way.