I cannot open Firefox 4.o nor can I unstall it. Help!

I installed Firefox 4.0 and received the popup message that computer must be restarted to complete installation. I restarted four times without success. The same message displayed at each click on the desktop icon. I attempted uninstall which displayed the same popup message. Next I did system restore to Mar 29, which put me back to version 3.06, but when I tried to open the browser, same popup message displayed. I attempted to uninstall 3.06 and it would not uninstall. The same message popup displayed. How can I get this junk off my computer?