my best bet is to crack open the gutz again and look through everything, get a mate with ya and just look through everything, it could be something wasn't screwed back properly, but why did u do it, u should have taken the caseing off and looked with ur eyes only...
ur ram may be seating in a wrong position
ur processor may be twichy
anything is possible, even if u take it to a computer person, not a retail person, but a "fix it" guy, the retail people brake it and get u into buying their computers with a fake copy of windows or mac, ( my experience )
cheers