In what ways can I use an external hard drive to extend the life of my computer?

I have a MacBook, only a few months old, and some one just bought me a nice portable external hard drive, and I was wondering how exactly I can use it to it’s full potential to help keep my computer healthier longer.

So far all I’ve done is sync in with Time Machine, since that’s what my computer seemed to want to do when I plugged it in.

I’m not a real heavy anything user (i.e. musician, movie maker, pc gamer). I mostly use the internet and word processing, and use garage band to record the occasional song. I also store a lot of music and photos on my computer. I only know that in the past after about two years my computers become rip-out-my-hair slow, and I’d like to do what I can to keep this one kickin’. I’d be willing to carry the thing around with me (it’s very small) if I needed to to store things on it.

Thanks buddies. Another probably silly question from me about computers.