What else besides the hard drive should I upgrade? I'm running 512MB of memory so I should probably step up to 1GB but besides that I really don't know enough about computers to know what needs to be upgraded.

First off internal hard drives are much cheaper. Yes they are faster as well. Do you have EIDE hard drive or SATA? Make sure you get the right one. Also yea upgrading to a gig is good, but you can usually find a 1 gig stick cheap anyways. I will guarantee that your system can handle at least 2 gigs. Depending on how much your willing to spend. Do you do any type of gaming? If so then upgrade your graphics card. I'm guessing you have an agp slot which means you can run up to an Nvidia 7600 which is a good card, but like I said this is only if you do any type of gaming.

check out the manufacs site and find out what ram it takes as well as the drive type brfore you order anything.

2 gigs of ram can be had for about 40 bucks is you hunt a little... look for kingston or corsair. ram is finiky and the cheap stuff comes doa alot. the harddrive should be all set assuming you grab the right type.

the only thing I would look at if you are really wanting to notice a difference is the proceessor it self but thats a little more of a job than ram and hard disk

sounds like you are on the right track

http://www.newegg.com/Product/Product.aspx?Item=N82E16820134046

be sure of the type you need forst but here is a good example of what you are looking for,