Firefox can't start -- thinks it's Internet Exporer

I have Firefox v1.0 on Win2k/SP3. Among other extensions, it has UserAgent 
Switcher, which is an indispensible weapon in dealing with websites which 
demand a browser that claims to be Internet Explorer.

Unfortunately, after a session with such a website, I shut down the browser 
while it was still spoofing IE. (Evidently, the checkbox that would return 
to the default user agent had been deselected inadvertently.)

Now Firefox won't start. Instead, I got an announcement telling me that I 
should not be using Netscape Java plugins with a Microsoft browser. That 
happened once only; subsequent attempts to start Firefox produced a little 
HD activity, but nothing more, not even the announcement. I can't open FF to
fix the user agent; I am in Catch-22.

The question is: How can I change the user agent without opening the 
browser? Alternatively, how can I override whatever it is that is preventing
the browser from opening, so that I can fix the user agent? If the switch is
in some file that I can remove termporarily, I would like to know which it 
is.

Thanks in advance...

-- 
Stan Goodman

All those who believe that the best physicians in France, given two weeks, 
can't diagnose what ails a patient - please stand up.