Everything seems normal in the BIOS. From what I understand 6 years on the same computer with no upgrades or repairs. That's most-likely to be the Power Supply going bad. You need to replace it soon; in some cases it can surge out and fry everything (from what I've read/seen).
If that's still not the problem then it's the CPU or Motherboard starting to give out. Either way, you can order a pretty cheap Power Supply from Amazon
. I would recommend a 250W to 300W power supply for a normal; everyday use computer.