Sweet another linux user. I use linux full time. I've tried the following distros but ubuntu is the best (make sure you use the 32 bit version!)
Gentoo
Fedora
Ubuntu
Suse
Mandrake.
I used each for about a year. I've been on ubuntu for a year and a half and it's by far the nicest to maintain.
If you have any questions drop me an IM. The system will be even faster when you aren't running off the live cd anymore. You can run both windows and linux on the same computer. I have to keep windows XP installed for work incase I'm required to telecommute in a crisis so it's on another partition. I can just pick if I want linux or xp when I boot up.
The 64 bit version of linux doesn't have alot of essential software ported to it yet (like flash!). So stick to 32.
I do everything I do on windows, aol, mail, web, play world of warcraft, starcraft, counterstrike source, ut and doom 3 and quake. I can help you set any of it up if you like.
http://www.novaslp.net/e17.jpg Thats a screenshot of my ubuntu desktop. I use enlightenment e17 instead of gnome. It's less of a system hog (not that gnome is bad compared to windows with antivirus loaded.)