On a XP System you can configure Mozilla as the default browser.
If you are at SP1, you can access the ‘Access and Programs’ Applet and configure the Internet browser…
I’m affraid you won’t succeed in removing IE from a XP System. Also you will get into very hot water… A tons of things could become incopatible… I really do not recommend… At lower OS, like 98 and Me, there were some applications which ‘allow’ the user to desinstall IE but, indeed, you will find a lot of trouble… 