We have a 300mb Seagate and a 300mb Maxtor external firewire drive for storing some of the raw imagery we use on our imagery processing computer.   Been quite happy with both.   We do not use any special software.   We took them out of the box, plugged them in, and another drive became available in My Computer.   We use it just like it was a permanent internal drive.

Like Chad, I would just pick up something at Best Buy, Comp USA, or whatever store might be closest to you.   I can't think there is any good reason to buy something like this from Dell.

Note the discussion below about ejecting USB devices to ensure that write buffers are flushed.