|Did you benchtest the board before installing it in the case?|
The only thing you can do to troubleshoot now is to remove or disconnect eveything from the board except the video card, one stick of RAM, & the keyboard. Remove all cards, disconnect all drives. Boot up & see if you can access the BIOS...if you can, immediately check the temps. If the temp keeps climbing until the system shuts down, you probably didn't install the heatsink correctly. If they look OK, run thru all the BIOS settings & adjust them as necessary to best match your hardware. Then begin reinstalling/reconnecting the hardware.