Blank (black) screen after windows 8 symbol.

I installed Windows 8 (from Windows 7) and things were OK.

Then I went to the Nvidia site and tried installing the latest driver because things looked a little strange
(nothing terrible, just some ragged edges).

Now when I restart, I see the window-pane image and the little circle thing that Windows displays,
then the whole screen goes black.
My computer is therefore dead in the water.

I tried rebooting from my Win 7 DVD, which brought up windows 7 setup screen,
told me to restart, which went right back into the Windows 8 and the malfunction.

Any ideas to bring this back to life?
Should I get hold of a Win 8 installation disk and boot from it? (I did the 7-->8 upgrade just
by downloading). Thanks in advance.

Not that it matters, but the machine is a Core I7 at 2.53 ghz w/ 8gb RAM (a desktop from Puget Custom Computer).

I have the same problem. When installing, got a message that there were some startup errors that Windows 8 was repairing by restarting. Now I get nothing but BSOD. Microsoft said that I need to buy the disc (clever of them). Any fixes that could be done by a normal human, age 66, like me? Many thanks.

Yeah, I gave in and sent the evil empire fifteen bucks for the disc. Now I have to wait for it in the mail while
my desktop is dead.
I find it unbelievable that such a catastrophic unrecoverable error is possible by a simple mistake.
I mean, couldn't the system be robust enough not to trash a display driver no matter what I do short of
hacking the system?

And why evidently is it impossible to even use Win 7 from my Win 7 DVD with Win 8 installed?
OMG, C'mon Microsoft!
(I just hope the Win 8 disc gets things up and running or this is a real mess.
I wouldn't want to have to format my C: drive and lose my software because of this.
(I of course have my data backed up, but I don't bother with my software.)