The BIOS screen appears before windows starts, so that means this is a hardware problem.
Sorry I was not clear on definitions. Here is a definition of power supply and motherboard.
The power cord on a desktop PC plugs into the back of a fist sized metal box called the power supply, usually abbreviated PSU. The PSU is inside the case, all you can usually see from the outside of the computer case is the place the cord plugs and the exhaust vent from the PSU's internal fan. The PSU converts 120V AC into 12V DC, 5V DC 3.3V DC, etc. It is not safe to open this box, but if it fails the entire PSU can be replaced for $50.
The Mother Board, abbreviated MB, is a big flat rectangle that internally has the equivalent of miles of wire sandwiched between layers of insulator. The CPU, sound chip, memory and many other parts are plugged or soldered onto the MB.
Please ignore the advice I gave earlier about breadboarding the PC. It was meant for someone who built their PC from scratch from parts.
Suggest you watch a few videos on youtube on building a PC. Desktop PCs are pretty standard in the way they are assembled. If after watching the video you are ready to disassemble your PC, debug the problem and then fix it you should create a new thread so that people see it. This thread is too old for anyone to see. When you open a new thread post the make/model # of your PC and give basic specs via cut/paste from a description of your PC. Then give the symptoms you have seen in the BIOS and the symptoms you have seen when running normally.
It's fine to decide not to work on your PC hardware. I used to change my car's oil, I do not do that anymore. PCs are much easier to work on than cars, but replacing parts may not be something you enjoy. Even if you decide not to work on your PC knowing what people think the problem is may make the PC easier to get repaired. You can also compare the likely cost of fixing your PC to the cost of a newer, potentially better, PC.
Good Luck.