MOB starting issue

Hi i tried to start my pc today, and well no screen or keyboard or anything, i looked at fan, when pc starts up it spins at normal pace, but then its slows down then after awhile switches off ( heat sink been really hot) now last night pc worked fine no issues, i havent even tried to oc this mother board, all i did was check few settings so it ran at what ever it needed, nothing that i did it was all on auto, been running super but like said last night it was running now it aint,\
System spec.
1x xfx 8500gt
1x 1gb ddr2 665 ram
2x sata hdd
1x gigabyte ga-8i945g pro
1x pentium D 2.8ghz
using gigabyte 360w powersupply

I think its cpu related, or could it be mob?? any advice please

Oh yeah, i tried removing HDD's and the graphics card but nothing, when boot system i dont even get light on my keyboard

i self built this seen im in i.t, mother board is few years old yes, power supply only just started using, i gonna take it into work tomorrow and test it on another lower watt power supply but i know it works off it cause i first double checked to see if it working off that, see i checked the heat sink...... but for awhile i noticed north bridge was very hot, so maybe my mob burnt out.... i got no clue see the system doesnt have speaker so cant even know what beep its doing, so cant say its ram or cpu or nothing

woould faulty powersupply also cause this issue?