The computers I'm trying to repair are just too far gone from over a year outside in a shed providing very little protection from the elements. I'm gonna buy new parts and make a PC with those and the few things I can salvage.
I'm trying out my first build using parts from two computers that stopped working. (I assume due to a virus or corrupted system/boot files) Both desktops originally would simply black screen after booting and loading windows, but the monitor was still getting a signal. I opened up an external hard drive and used its adapter to get a recovery file to try to restart the computer. After it finished copying to my laptop, it had the same problem. I formatted the hard drives with the problem and put them back in the PC. I got a windows 10 iso and booted the computer fine it then went to a windows download prompt. I had to go to work for a few hours before configuring. When I came back I moved the desktop into my room and now it starts up and runs the fans and LED lights, but nothing else happens.
Troubleshooting I've done so far:
Cleaned out the graphics card, the entire case and the mb with pressurized air.
Changed the ram sticks (all four at a time)
Swapped graphics cards
Reset the BIOS (by reseating the battery, using the jumper pins, and pressing the CMOS reset button on the mb with that option)
Swapped out the internal hard drives
Tried different outlets
Tried different cables, different video connections on desktops and different inputs on multiple monitors. (All monitors are working with other computers)
I have tried two separate PSUs, at least one was working before this problem. I have also tried two separate mother boards.
Thank you for taking time to read all of this. If you have any ideas or general tips please let me know.