no post beep (power on self test) means either one of two things (or maybe both but thats unlikely)
your motherboard is toast
your cpu is toast
(actually there is a third option) ... (there is a speaker hooked up to your mother board isnt there?) (im assuming there is and you've heard a post beep from that computer before)
try replacing the cheaper one first ... (usually the cpu... as you can find a slower cheaper cpu that fits in a LGA 775)
here's one for $38 bucks
Newegg.com - Intel Celeron 430 Conroe-L 1.8GHz 512KB L2 Cache LGA 775 35W Single-Core Processor - Processors - Desktops
make sure you can return the processor!!!!
(maybe get it from somewhere else?)
(you dont want to spend 38 dollars for nothing do you?)
or if you can get a LGA 775 socket cpu from a friend that would work...
if that doesn't fix it try a new motherboard (and buy the on that suits you upgradeable is important)
try both processors in it... and if the processor (the quad core that is) doesn't work ...well... time for a new smoking processor as well...
just make sure it fits the the zif (zero insertion force) connector
LGA 775 fits... others dont
good luck ... i think you might be right the mobo is probably toast .. but make sure its not the cpu because it may be under waranty
or maybe the mobo is under waranty... (btw not enough information there are a lot of nforce 750i sli motherboards out there... )
check this out lol
750i sli motherboard - Google Product Search