Have you got google desktop? If so, all but the very latest versions conflict with IE7. Update, reboot and all will be well.
Also, if you had other programmes running during the install, (Skype in my experience) that can adversely affect IE7.
I resolved it by uninstalling, (very easy), switching all other programmes off and re-installing.
After the reboot you can now switch on all other programmes.
I use Firefox for 98% of my browsing, and dislike IE with a passion. However, IE7 is a huge improvement on previous versions, so it is worth persisting with.