So you pulled that cramped old 40GB hard drive out of your notebook and replaced it with 160GB of storage goodness. Ever wonder what you should do with the leftover drive? Simple: stick it in an enclosure and use it as a portable USB hard drive.
You supply the drive; Meritline.com has an enclosure for just $10.99 shipped (after entering coupon code HW1971413OFF, which expires 1/25). It's compatible with all 2.5-inch IDE and SATA drives, and it includes both IDE and SATA external interfaces (cables, too). You also get a carrying case and a little screwdriver for opening and closing the enclosure. The drive itself gets powered by the interface, so there's no need for an AC adapter.
For 11 bucks you can get yourself a terrific little portable hard drive for transferring files, on-the-fly backups, and so on. Sweet.