It was just one thing after another.

So first my GPU wasn't being recognized. I tried a lot of things, including trying to install windows before realizing I needed to pay 100 euro for a license, so fuck that. Then I tried resetting my BIOS by removing the CMOS battery, which worked, but then my computer wouldn't boot. Then I reseated the hard drive and it booted, but only with the display plugged into the GPU. Then the mouse was really floaty and had input lag, so I changed to a wired connection, which did nothing, but then I went to BIOS settings and did nothing but somehow it fixed it. Now as far as I can tell, my hardware is all working, but when I launch steam, it seems like it keeps trying to launch but just doesn't. It's hard to explain, it's like if I launch steam, nothing happens, but then after a few seconds the screen "jumps" as if a new window had been opened on top of what I was already doing, or like I've been tabbed into another window. I'll reinstall steam tomorrow, because I assume it's a software issue.