USB Drivers Issue

So, I was attempting to update my USB drivers yesterday and now find myself in quite a pickle. I downloaded the update from my motherboard manufacturer and ran the exe. I was vaguely watching the process as I have numerous times, and it had just completed the step whereby the old drivers are uninstalled/removed. Just before it began installing the new, updated USB drivers, Windows 7 wanted to make sure I wanted to do that, and threw a security popup asking if I wanted to proceed... If you haven't found the irony in this yet let me point out that I could not use my mouse or keyboard to tell Windows that I did in fact want to proceed. After trying all the USB ports, I admitted defeat and thought my last ditch hope was that whoever programmed the driver update exe would throw something in to revert back to the old drivers should the computer get shut down mid-update. Turned out to be wishful thinking.

So, now I'm stuck without the ability to use a mouse or keyboard outside of BIOS. To complicate matters, I have a login password set up in Windows and can't even get to my desktop. I think if I could at least get to the desktop I could resolve the issue, as for some reason an old mouse I had lying around does seem to work in one of my front USB ports, but it is only that mouse that works there (i.e. keyboards and other mice do not). So, if you know a way I can install some old, temporary USB drivers or get passed my login password, you will have my gratitude, as I would really not like to have to reformat.

Thanks for any help/suggestions/advice.