I just downloaded Firefox which was working fine. Then I downloaded Thunderbird and imported my mail. Now, Firefox will not open. Clicking on it only opens Thunderbird. Any ideas?

Have you tried getting to the browswer through Start Menu Programs? Life is more painless for those who are brainless.
Which browser have you set as your default? Firefox or Thunderbird? Maybe I'm wrong but I'm guessing you made Thunderbird your default and so now everytime you want to open a web browser it opens up Thunderbird because you set it as your default. Sometimes computers do that. You need a good defence if a trojan barges into your territory.
Vi, Thunderbird is not a browser. It's an email client. Life is more painless for those who are brainless.
There is a routine over at the Mozilla web site which is similar to your problem. It deals with bleeping out certain portions of items within your registry, then reinstalling. It is a big search there to locate such, but you will spend a good twenty minutes finding the routine and the file names needing to be bleeped out. If you do not bleep these out, essentially nothing will change. Wm.
