I'm not a mind reader mate, as I said, without ANY pertinent details such as the details asked for in the FIRST STICKY thread of the forum, then it is IMPOSSIBLE to say, especially not knowing what PSU etc etc etc etc is in the system.
It is also IMPOSSIBLE to say if the overheating caused it, as I don't know what temperature it reached due to an inherent inability to mind read or travel back in time / teleport to another time/place.
If you wish more comprehensive help on the matter, then I highly suggest providing ALL relevant details as per the STICKY thread.
It sounds like it's dead though.
AM3 965BE / Corsair H70 / 4Gb Corsair XMS3 2000Mhz / GigaByte 990FXA-UD5 / Corsair Force3 90Gb / x2 HD3870 Atomic Edition / x4 1Tb Storage & Momentus XT 250Gb / Sony AD-7700 DVD-RW / Auzen X-Mystique / Enermax INFINITI 650W / Lian-Li PC-7FNWB / Logitech X-530 / Logitech KBoard & MX620 / Logitech C525 / Epson RX685 / DELL U2312HM