I think you can buy a WD 160GB or up IDE harddrive (with 8MB cache), and install this drive with the USB harddrive enclosure. The following is the pictures showing 2 types of the USB harddrive enclosure:
(Those 2 are my collections, hope the picture can help you to know more.)
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This USB2.0 harddrive enclosure is for 2.5" notebook harddrive, and it's small.
It just needs the USB cable only, does not need extra power supply (like power adaptor).
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This USB2.0 harddrive enclosure is for 3.5" IDE harddrive(normal harddrive for desktop computer), and it's kinda cheap in the market.
It needs USB cable and power adaptor.
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For the harddrive, I just trust on WD and Seagate since they both offer at least 3-year warranty, and those 2 brands have less return rate.
*The CD is just for you to imagine the size.
*Sorry that there's a couple dead link, just get it fixed!