If you go to www.litepc.com they have a product called "XPlite/2000lite" which might help you out. Instead of paying for it, you can just use the Free Trial version.
What does XPlite/2000lite do? It takes standard Windows un-uninstallable features and transforms them into optional components so you can install & uninstall ANYTHING easily. Hopefully this should help you with your failed IE 7 uninstall by repairing the uninstall routine.
Even if the IE 7 uninstall fails again, "XPlite/2000lite" doesn't make substantial changes to your system. All it does is to give you access to previously unaccessible install/uninstall program routines.
By the way, I don't sell this stuff and I'm not connected with it in anyway, except I've been using "98Lite" (98Lite is for Windows98, 98SE, & ME) for about 5 years now with no complaints at all.
They have NO spyware, malware, or anything in their products; including their free stuff!
LitePC has a free product called "IEradicator 2001" with removes ALL traces of Internet Explorer, but it's only for Windows 95, 98, 98SE, & ME because these Operating Systems don't depend on IE browser engine like XP does.