Help! Browsers won't start

I have an older Toshiba laptop running Windows 2000. I was using Firefox one morning, went to doctor and when I came back none on the Browsers installed on it would work( IE6, Netscape, Firefox). Deep Scans w/ 2 antivirus programs found nothing. I've changed firewall settings, and even disabled. check the Registry for things loading at startup, etc. Nothing. When I try to open any of the browsers, theres a period of disk activity, then nothing happens. If I go into Task Manager it shows the process (e.g. firefox.exe), but no activity. No unexpected entries in Task Manager. If I start it in "Safe Mode w/ Networking" Firefox will open, but gives "Page not Found" errors. I can get IE to open if I go to Calculator and go to "Web Help" (But I can't download anything, this was a pre-existing problem, I have not used IE in months), so port 80 is working. I reinstalled Netscape (I still had the Install on this machine) but that changed nothing. I've tried/checked many other things as well that I found here and on other "Help" forums although none were for exactly the same problem. Most probably/obviously I caught a virus, but which one and how do I remove it and fix the problem. TIA for any help anyone can give me.

Most probably/obviously I caught a virus, but which one and how do I remove it and fix the problem.

Hi and welcome to WTT forums, if you think you have malware then its best to go here
http://forums.whatthetech.com/Are_you_Infected_t106388.html
and follow the instructions carefully.
One tip for you, when you have posted your logs in the correct forums please don't make a "follow up post" until you have received a response…..the malware fighters look first for Zero response topics…..
Good luck and the compliments of the season to you.
Regards
paws