Updated nic driver...now I'm locked out

I updated the nic driver and now when I try to log the pc onto the network...it doesn't recognize the username and password (hasn't changed) and will not let me proceed, cancel through the log in screen or anything. I tried reinstalling win98 but that didn't work. Any suggestions? I've tried finding a "go back" software to run from DOS but had no luck.

If the problem started within the last 5 days, then press and hold the Ctrl key during startup, select 'Command prompt only', press Enter, at the C:\> prompt type scanreg/restore and press Enter, select a Registry that predates the problem, and press Enter.