3.3v 12v?

[Deagle]

Could some1 please explain to me what do those things mean on a powersupply and how do u calculate how much power u need?
Thanx:p

[Reid]

Yes, but somebody put a guide together that explains it better than I could: http://firingsquad.gamers.com/guides/power_supply/default.asp

[Budfred]

And here is another big bunch of information (http://members.shaw.ca/need4speed/Power%20Supply%20Choices.htm) about power supplies....