vista won't recognize external hard drives

I just bought a toshiba satellite L505d-S6947. Got home and hooked up my two western digital external hard drives. One is a 250gb and the other a 500gb. The laptop did not recognize them at all. No new hardware, nothing. However, they did work on my desktop about a month back. They havent been on since then. I was just wondering the solution to get these things to work. Thanks