If it's run fine for 3 weeks and this just started, I doubt memory timing, ram voltage, bios updates are the problem. If it needed a bios update, it wouldn't boot. If the ram stuff wasn't right, it would have issues sooner, so lets use some logic and eliminate those.
Could be a driver issue as stated. If windows update did an update for one of your drivers a few days ago, possibly the sound one as mentioned.
If it was heating/PSU/etc, they probably wouldn't be getting program not responding messages, it would either bluescreen or shutdown or freeze.
I would tend to point to either an update a few days ago, or malware viruses.
Program hanging and then coming back usually means something is lagging the system out, not needing a BIOS update or bad RAM timing and either of those things don't start weeks after it's been running.
Try downloading HWmonitor. IT will let you see your temps to rule that out, and also check your task manager to see if your CPU usage is being used up by something in the background.