Hey man, sorry the upgrade didn't go smoothly! There's two things to do here.
First: Put the old heatsink back on, and try it. If it runs, nothing got shorted, everything's fine.
Second: If it doesn't run, don't panic, because: Did you take out your cpu when you removed the old heatsink? If so, you may well have forgotten to close the locking mechanism on the socket. It's the little piece you have to use a flat-head screwdriver on to move, and when in the "open" position, the computer should power up, detect failure, and power down. All very rapidly. It sounds like what you described!
Let us know if either or both of these steps works.