External Drives Won't Show Up

Hi, I have a 1 year old Macbook running Snow Leopard. Recently my external harddrives stopped showing up when I plug them in. I went to finder preferences and made sure they should show up on my desktop. I tried reformatting and repartitioning one of my jump drives through disk utility because it showed up there but it still does not work. I have tried 4 different drives and none of them show up on my computer but they do show up on other computers so it is something wrong with the computer. The USB ports do work however, because I am able to print through them. Any help would be greatly appreciated.

Are they getting power from the USB ports?