In Tools > Program you have to click the "Select programs" button. Then in Vista and Win 7 a new window opens. I'm not sure if that applies for XP.
If so, the new window is "Default Programs". Then you select "Set program access and computer defaults", and in the next new window click the double down chevron arrows for Custom.
Select your defaults from there. I don't believe this works for web based email access.
I have Internet Explorer 8 on my Windows XP computer. When I go to Tools/Internet Options/Programs/E-mail how can I choose which e-mail program that I want to put there? Thank you very much. user470