I am assuming you HAVE NOT dropped this external drive or otherwise subjected it to a physical jolt.
The topic title says....
Imation Apollo25 PHDD-320
but it's actually
Apollo 25 PHDD-320 - it has a conventional laptop sized (2.5") hard drive inside it
External hard drives with conventional hard drives inside of them DO NOT require any special drivers - they use generic drivers that are built into Windows - but you DO need to plug them into a USB port (or two USB ports) that can supply 500ma of current and that recognizes the external drive properly otherwise.
E.g. if you plug it directly into a USB port that is built into your netbook's case, it will probably be recognized fine and Windows will install the generic drivers for it.
Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1: