Re: Doesn't power on
Did you at least unplug the PSU's power cord from the computer? I would recomend you always do that before swapping any hardware. Is there a primary IDE drive other than the new SATA? If so, make sure the jumper is set correctly. If still no power, then it is possible that static could have zapped the motherboard.
Random movie quote to make you seem hip and "with it":
"Please take the chairs away. I don't like them. The big one is staring at me and that short one is being very droll."