While you can always follow the steps mentioned at Reset Internet Explorer Settings or RIES feature of IE., you can instead also download and apply this Fix It from KB923737 to reset Internet Explorer instantly!

Do note however, that this fix does not work in Windows 7. Instead, you can use the Internet Explorer troubleshooters to achieve this automatically.

By default, Windows 7 has two Internet Explorer troubleshooters on a new installation. These are Internet Explorer Performance and Internet Explorer Safety. To access them, open Control Panel > All Control Panel Items > Troubleshooting > All Categories.

You can see all the Windows 7 troubleshooters at Troubleshoot & fix computer problems in Windows 7 natively | The Windows Club