I would highly recommend updating windows xp to the sp2 version. Then install the ie7 beta 2 for xp sp2.
also, if you want to uninstall IE 7 beta, go to the control panel - add remove programs - and place a check mark on show updates at the top right of that window. Then find the ie7 update for internet explorer and select remove. That way you will have the previously working ie6 back on in action.