Having gone through the upgrade process the pc rebooted and displayed the logo then went black just at the point of displaying the login screen. The,monitor then popped up a message saying 'Input not supported'. The problem now is I can't do any of the suggestions in other posts as I can't get to a screen that displays anything like install different drivers (they were up to date anyway) and it isn't reverting to Windows 7 by itself.
What can I do to get a working pc again? Would a newer graphics card work? The current one is an Nvidia GeForce 7900GS.
All help gratefully accepted.