Bitcoin Mining

[cyberthane]

Hello!

I have done some research on Bitcoins. I have a couple questions pertaining to mining that I hope you guys could help me answer. I am starting to buy tower desktops so that I can get some mining machines going. My first question is, though, if I install multiple graphics cards, can each one of those cards mine?

My next question is, are there any good resources on setting up a mining machine? What OS is preferable for mining? Any help here is appreciate. Thanks!