First upgrade your PC. A 533 mHz processor is wayyyy to slow for todays audio processing. While your at it, get a fast HD (7200 rpm +). You should be fine with the RAM if it works w/ the new computer.
Also, get an external audio interface (
Tascam US122,
US224,
US428)< all USB. or equip your computer with firewire and get a nicer interface (firewire supports more inputs, which sounds like what you need. For USB, you can only record 4 mics simontaniously, where as with firewire I believe it can be 8+ mics). If you need real faders to mix with, consider that in your purchase. I really like them, it helps with the mixing by mouse boredom.
Since you sound like you need a complete rig, go no further than www.tweakheadz.com . that'll guide you through everything you need to get started as a newbie, as well as some tips on recording, and cheap products.
good luck, repost if Tweak doesn't answer your questions, or if you have any others
thesparrowband
