USB External Hard Drive With PS3!!!

I have just bought an external hard drive for my ps3 (laptop or whatever it works with cause i need space) and i cannot get it to be compatible with my ps3!!! i see the circle on the top right of the screen on the ps3 when i connect the 250GB HD, but it just does not pick it up!!! CAN I INSTALL AN EXTERNAL HD? It's a Seagate, if that helps. I heard I need to format it to FAT32 but i cannot get it to FAT, or FAT32, just NFSTC. Kill me? Is there a way to format it to NFSC or whatever.