"If you are having problems with Internet Explorer 7 hanging, crashing, silently closing or other bizarre behavior, an incompatible toolbar or other add-on maybe involved. The fastest way to determine if an add-on is causing the problem is to run Internet Explorer 7 with no add-ons. You can do this by going to Start, clicking All Programs, click Accessories, click System Tools and click Internet Explorer (No add-ons). This disables all add-ons from loading in that instance of Internet Explorer. If the problem goes away, you can manually disable all the add-ons and then enable add-ons one at a time to find the specific one causing the problem. Below are instructions on how to manually disable a specific toolbar and a list of known incompatible toolbars that can cause serious issues with Internet Explorer 7" per
http://msdn2.microsoft.com/en-us/ie/aa740486.aspx
If you can, in Internet Explorer open Microsoft Live OneCare and run a "full scan"
http://onecare.live.com/site/en-us/default.htm
A last resort would be to uninstall IE7 from ad/remove programs.
Reverts back to an version IE6.
Run a Microsoft Live OneCare, "full scan" and restart before reinstalling IE7.
You can not uninstall IE7 on systems running Vista without reinstalling Vista.
http://www.microsoft.com/windows/products/winfamily/ie/default.mspx