I've got a couple of years old custom PC and recently ordered a new HDD for my daughter's computer. I wanted to format it and install Windows on it, so I created a new bootable USB and hooked the new HDD up to my PC to do the install. After formatting and installing Windows on the new drive, I switched back to booting from my original SSD and removed the new HDD. Now, my PC starts up but shuts down after a few minutes, or it sometimes runs but the monitors stay black and show no signal. My setup includes a Tomahawk B550 motherboard, a Crucial SSD for the boot, an M.2 SSD for storage, and a 2070 Super GPU, powered by a Focus power supply. I should also mention that I can't put the HDD I installed Windows on back in since it's now with my kid out of state. What's going wrong?
2 Answers
So, just to confirm, your PC doesn't boot at all now after removing the new HDD? That's a bummer! It might help to put the original hard drive back in if you can, but I get that it's not possible right now. Maybe double-check your connections? It's easy for something to come loose when changing drives.
Are you getting any kind of display at all when you boot? It sounds like your PC isn't fully getting into Windows since the monitors are showing no signal. Can you access the BIOS? When you installed Windows, did you unplug your original SSD or just change the boot priority? That could make a difference when you took the new HDD out.
Yeah, I edited the original post to clarify that the tower powers on, but the screens remain black and say there's no signal. I didn't unplug the original SSD; I just changed the boot sequence to the flash drive and installed Windows on the new HDD, then removed that drive and the USB after the installation.

Yep, that's right. It just shows no signal and sometimes it shuts down. I really wish I could just pop that new drive back in, but it's unfortunately out of state.