Oh, hi, Mark!
This girl is at the end of her rope. Recap of previous post: my mouse pointer got unusably slow. Next day PC wouldn't work. 1 long beep, 3 short.
Changed the graphics card, nope. Just changed out the motherboard, nope.
So I did a lazy research because it takes a lot out of me (back problems) and I was tired. Turns out if you don't put the company in the search all kinds of stuff pops up that says gpu or insufficient RAM problem.
Why, if nothing changed in those 6 months it worked, would it suddenly need more RAM?
I have 2 sticks of 8GB but the original motherboard only recognized 1 stick. I don't recall having a limitation the 10 or so years ago I built my last desktop. This motherboard apparently only recognizes 12. Am I crazy thinking a gaming motherboard should not have a limitation like this?
Quick googling says that 1 long beep and 3 short beeps means the RAM is not working correctly. One of the two sticks might have failed. Try the machine with one stick at a time.
Those error "codes" might be manufacturer specific. Try to google "1 long beep and 3 short beeps" and your motherboard manufacturer.