Getting yourself more RAM is the easiest thing (and the cheapest) to improve your computer's performance. If you've only got 170 Megs of RAM, I would look into upgrading that. I personally have 640 Megs of RAM, and know plenty of people that have over a gig of RAM. One place to shop for RAM is at crucial.com.

As for the hard drives, no there is no reason you shouldn't get a larger hard drive. I haven't ever personally upgraded my hard drive, so I don't know about size issues as far as installation goes. If you have FireWire, look into getting an external hard drive.

Edit: I just noticed you said you're running Windows ME? Get rid of that if you can and get yourself XP or even just standard 2000. ME is widely regarded as the worst Windows operating system ever created. That will probably also help your computer out.

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