To give an accurate answer you'll have to be more precise.

What mixer are you using?
What software are you using?
What soundcard or interface are you using?
How many tracks for drums and guitar?

The computer you're recording with has nothing to do with your question. Any modern computer can record a drumset and a guitar if the rest of the stuff is right, like your mixer, soundcard and software.

OK so im using G5 mac
with garageband wich it came with- i know i probably need a differnt program.

I have an Alesis MultiMix, 8 channel w/ USB.
And i dont know about the sounds card, its the stock G5 Mac OSx card. srry

And it would be great if i could get the 8 channels into 6 tracks but just drums on one track and guitar on another would do just fine.

your soundcard would be the alesis, unfortunately that device is only capable of 2 tracks 1 left 1 right if you pan the drums hard left and guitar hard right you can record 2 mono tracks to your comp.

ok ilkl give it a try and keep u posted how it goesclass="xf-ul">