So about 2 years ago I bought a Dell Optiiplex 390 for $100 from a yardsale, and it sat in the corner of my room for awhile due to the os being corrupt. I decided a few days ago to try and make it working again. I formatted the 250GB hard drive, put the windows 10 installer on my flash drive, and installed windows onto it. It worked for about 10 minutes, and then suddenly stopped giving video signal. The monitor had no signal and the computer was still running. I let it sit for a little while, but nothing happened. I then shut down the computer by pressing the power button once, and then tried restarting it. The monitor lit up with the dell loading screen, then to the windows 10 loading screen, and then no signal. I also tried installing windows 10 on one of my portable hard drives and running the computer off that, but the same thing happened. Every time the computer is turned on, it stops outputting as soon as windows is loaded up.
Needless to say, I would appreciate anyone's ideas about what is going on.