Windows 7 came packaged with IE8, so it is a feature that can be turned on or off, not downloaded. The download of IE8 is for Windows XP and Vista.
Control Panel\All Control Panel Items\Programs and Features
Open "Programs and Features" then look to the left for "Turn Windows features on or off". You may need to turn IE off and reboot before you turn it back on. I'm hoping this will fix your problem. If not, let us know and we will try something else.