In order to start Internet Explorer 7 with no add-ons do the following:
Click Start -> All programs -> Accessories -> System Tools -> click the IE icon (with no system tools)
or
Start -> Run -> type iexplore -extoff then press Enter.

This can be very useful if your browser crashes or fails to launch, you can start IE7 with no add-ons and then go to Tools -> Manage Add-ons -> then remove all of them, restart IE7 and then add them one by one to see if one of the add-ons causes the problems.