In those cases where I need a larger drive I rather use the new 2.5″ pocket hard drives that are available. These are essentially laptop hard drives in an external enclosure that run off of USB 2.0 power. No need for an external power adapter.
Why are these drives handy? Well you see, most cheap laptops come with very small hard drives and this is a cheap way to expand your storage capacity. I use my external drive to hold all my test virtual machines which take up quite a bit of space. You can also easily attach the drive to your laptop by using double-sided velcro to stick the drive to the laptop. This way you have a nice portable solution!
I recently bought a 500GB SimpleTech 2.5″ drive from Best Buy and it works great. It also has a second USB connection you can use to plug it in to the laptop so you can increase the amount of power that feeds the drive. This allows you to see the drive on laptops where just plugging in one of the USB connectors doesn’t seem to work.