It would be nice to know more about your computer, such as the operating system etc. In the meantime...
You have two options...If you DON'T want Firefox to be installed, then simply uninstall it, then open the Control Panel, double click on the "Internet Options icon, then click on "Programs" tab and place a CHECK mark in the box at the bottom of the screen that says: "Check to see that Internet Explorer is the default browser". Click on "Apply", then OK. That will cause the links to be opened by Interne Explorer when Firefox is uninstalled.
If you want to leave Firefox installed so you only use it occasionally, do the same thing in "Internet Options" above. Next, open Firefox, then click on "Tools" in the upper left, choose "Options" from the menu. When that loads, click on the "General" tab on the left, and UNCHECK the box that says: "Firefox should check to see if it's the default browser when starting". Click on OK>
Hope this helps.
I downloaded firefox a few weeks ago, didn't like it because it was too confusing for me, uninstalled it and ever since have been unable to open links to IE from e-mail. I finally figured out that I need a firefox.exe to do that. So, I downloaded firefox, was able to open links, then when I uninstalled it the firefox.exe was expunged. Does anyone have any idea how to keep the firefox.exe without actually USING the browser? I'm sorry if this sounds confusing and idiotic, but I'm a newbie!!!