This has been asked before, I know, but I haven't yet found a definitive answer to how to fix it without deleting my stuff. The problem is that Windows boots normally, goes to the normal Windows loading screen (which took far longer than normal, mind you) but then booted straight to a black screen. I clicked and my cursor appeared. Ctrl-alt-deleted, no response. Waited a while, still nothing.
I HAD installed a major Windows update recently. (~8-16 hours previously between downloading and installing)
Sorry about that, everyone. I left my PC on overnight to do a RAM scan, I was stuck for things to do. Got up in te morning, turned it on, same old blacks creen with cursor. So I turned it off, made sure all connections on my motherboard were snug and firmly pushed in, especially my GPU and HDD. Turned it on again, went downstairs to make this thread on the auxiliary PC and whaddayaknow, came back upstairs and my PC was working fine. I doubt that was the root cause, most likely my hashed job at attempting startup repair actually worked.
Download c-cleaner and/or auslogics registry cleaner and run it to be sure you haven't left cruft in your registry. If your machine is now operating at peak the way you want it, set a system restore point so you have a good fallback position.