2- Maybe your hardware has gone bad. To test, download prime95 and run its torture test.
www.mersenne.org/freesoft.htm
If Prime95 reports errors, it would indicate a hardware problem. From there you would install a monitoring utility for your motherboard... it will show if the voltages are out of spec, or if a part is overheating. The best utility is that one from your motherboard manufacturer. Not all of them make one available. If so, try motherboard monitor or speedfan.