hey,
Do understand that IE 7 is not so compatible with XP.( Coz its BETA Version)
It is compatible with Vista which is yet to be released.
As said earlier you can uninstall it via Add or remove programs (Appwiz.cpl)
by checking "Show Updates".
Then you can install IE 6 from the microsoft support page.
Dude try not to delete the IE -7 folders(files) or try not to do a repair
installation before uninstalling IE 7 from Add or Remove programs.