Not much hardware info so here goes...New install of a few weeks old huh.
Did you install a virus scanner? Virus can do some <mod edit> things to a bios and a system.
Have you run memtest?
Seeing the CPU is at 100% usage did you open resource monitor to see what is running? What is taking so much CPU usage?
IF this is a new system or you fiddled with the cpu, it could also be cheap thermal past has failed. I recently put a Xeon in an old Socket 775 MB and used the thermal past they sent with the Xeon, SILLY ME! Temps were in the 60's to low 70's when idle within days and slowly climbing, so I replaced it with the good stuff and now in the 40's to 50's. I need a better cooler than the stock core 2 duo cooler I know but at least the new good quality paste made a difference of around 20 degrees. Your cooler should be fine but if the builder used cheap paste that could be a factor along with a virus.
Without more hardware info it is hard to say what else it could be. Check ram compatibility on the Motherboard page but as it did run for a few weeks (Assuming new system?) I doubt that is it. Is all the ram still showing up? Could be a couple of things contributing to this. Failed ram maybe? It happens.
Hopefully someone with more experience can help but I would check those things I mentioned.
Unsure if you have a new system or just a new Windoze install makes it hard to work out what is going on.
More details of whether a newish system or just new Winblows install and your hardware specs in your next comment please. Ram brand, certified speed, timings, Cpu and Motherboard etc. Are you overclocking? and if so to what? Have you done any Hard drive checks? Is it an SSD or HDD or both?