Hi
maizenbluedoc,
Welcome to the Windows 7 Forums. I don't know what you can do, in the editing the registry part, but at least to access the computer (after the login), your best choice is to boot into safe mode, and probably do a system restore from there.
Carefull, as system restore from safe mode can NOT be undone!
Here is a guide by
Ian on how to boot into safe mode:
https://www.w7forums.com/safe-mode-t1497.html
Basicly, you reboot you PC, press F8 the moment something on your screen, and stay pressed until you hear a
"Beep!" Then just choose "Safe mode" in the list using the arrows and then press enter.
Ian's post explains more in detail.
That will boot into a windows with only the essencial drivers loaded.
Warning! The fact that only the core drivers are loaded will make windows look like windows classic, and that might stop some of softwares from working properly, or from working at all.
Hope this helps!
Fire Cat