So, as background, my desktop runs Windows 7. Yes, I know, it's archaic, ancient, blah blah install Windows 10 etc. And I might, if nothing else works. But I'd prefer not to. So here's the rundown.

Previously, my machine was running using this motherboard. it worked for a while, until it didn't. So I bought new parts, replacing the motherboard, RAM, and the processor. The new board was this and the new processor was this. Now, the problem that I didn't know until now is that these parts aren't the most Win7 compatible, as there's a USB driver issue. After getting through several hurdles and flashing the motherboard BIOS to the latest version (that allegedly fixes some USB issues), I've come to a point where booting reaches the login screen, at which point all of my mice and keyboards stop working. This happens on the login screen and on repair or reinstall screens, making it impossible to proceed through them. To make matters worse, the motherboard doesn't have a PS2 connector I could use instead (unless using a PS2 to USB adapter would work?). This likely happened because I installed the OS on a different processor and chipset.

Does anyone have any fixes? preferably something that lets me use things as is, but if there's really no saving it, I'll take backup and upgrade advice.

Fiddling with the BIOS hasn't helped any USB issues, it's likely a driver issue.