I had a computer that the mother board bridge kept over heating on me. so I opened it and had a fan blow into it. worked fine for a while, then the mother board decided it had enough and blew up on me. sparks flew out, it was cool..... but it might be the cpu overheating. I built a computer and used the stock fan and it just wasn't enough for it. it was getting really hot and hitting the failsafe and shuting off. that might be it. if your mb has a heat sensor I would check to see what your cpu core temperture is. you might just need new thermal greese and cpu fan. or it might be your powersupply going out on you.