first of all, unplug your reset button from your mobo
check for blown/leaking/buldged capacitors
after that, test your psu (at work we have these really cool psu tester things, oppose to sticking voltmeter-things in all sorts of places)
note: just because a psu tests fine(voltage wise), doesnt mean its not faulty!
reseat all major componenets: cpu, ram, vidcard, check/replug and preferably swap cables(ide/sata), swap out ram and try different slots etc.
after, if still no go, try your general trial-and-error till you are left with nothing..
with the thermal compound - there shouldnt even be anywhere near enough placed on the cpu in the first place to be able to leak onto the board....
in regards to sli: afaik, you should just be able to plug ur vid card straight in and go from there (i have never setup sli or even used a pc that is using sli so sorry for my mis-informed advice