TSGL: Changing browsers

[Sylvia Gould]

My computer is set up to automatically use Firefox. However, I find many 
times only IE will open a particular website. I was told there is an icon 
somewhere to switch browsers "in midstream" but can't locate it. I have 
tried copying  the address in a newly opened IE address bar, but that 
doesn't always work. Where do I go to make IE my default? Thanks.
Windows XP, Home Edition
Sylvia Gould