Now there are many vital things to look at when buying an external hard drive. These include the connections, the size fo the drive and the power supply to the drive i particular. Now the connection is usually either firwire or usb. Personally i like usb better as it can be used more widely however apparently firewire is faster so hey, personal choice. Now the second thing to chec when buying an external hard drive is the size of the drive. Now most drives are actually transferable so you can put a differnent drive into the case later however when you can buy a 300gb or 200gb for hardly any more than a 120gb i say why not. You may as well just buy a ridiculously bg drive so that you wont run out of space unless you use a lot of videos or whaever. The third important thing to look at is the power supply. Now unlike usb sticks, hard drives have moving parts and thus they use a lot of power. Most drives need to be plugged into the power supply however there are drives available that do not to to be plugged in. The only limitation with these are that they are usually only about 40gb so not that useful for storing lots of stuff. However they are a lot more useful in that you can store movies on them and watch them on your laptop in the car or when camping and as you don;'t have to plug them in. Once again it comes down to personal choice and needs. Drives cost between one hundred and five hundred dollars. The really cheap ones are just a case and smallish drive. The msot expensive ones are either a really good brand with warranty or really compact and 'plug -in -less'. I chose one that is 200gb and was about 160 bucks. i have had some problems with it but it has been great particually for my music collection as i would need about 3 ipods to hold all my stuff.
I can reccomend you buying an external hard drive but just think about these differnent things as they do make an impact on your purchase.
all the best you ebaying partners
and may the mighty eagles win!