you also gotta eliminate all those useless windows services running in the background... they suck up all your power! goto start>run>services.msc and start setting things from automatic or manual to disabled. How do you know what to set?

http://www.dead-eye.net/WinXP%20Services.htm

you should dedicate this computer to recording and forget about ever using it for internet or games. Perform a fresh formatting/installatin of windows and delete any software that isn't needed. eliminate absolutely everything you can. It wouldn't hurt to upgrade that cpu/mobo and get more ram.