Aside from the memory and video card, you're computer isnt THAT much crap. Unless you're editing videos and what not, 1.1 gig of CPU speed, should be enough. What you need to focus on now is a better vid card, 512 megs of memory, and another hard drive.

As far as HD's are concerned, you can get a 100gig HD for 100 bucks if you look for Buffer speeds of 2 megs to save 15-20 bucks. I got my ass a 100gig Western Digital for 80 dollars. And unless you are REALLY looking you arent gonna notice anykind of difference. I've had the computer running around in hoops looking for info and have yet to see a 75% change.

And if you have CABLE and AOL/DIRECT CONNECT look for ways of improving that Operating System (Although ME is pretty darn good).

I currently run:

AMD 1600 (runs at 1gig though, freezes up when I up the speed, might have to look into that - dunno much about changing speed in BIOS)
100gig Western Digital XP (replaced a 60gig that I used, abused, and mistreated for a year)
30gig Western Digital ME
640 megs SDRAM (I've yet to see a convincing argument for spending 40 dollars extra for DDR)
ASUS K75A motherboard
PACBELL DSL (900-1100 connection speed)