Uninstall Itunes (deactivate your accnt first on it) Make sure Itunes folder is totally gone in My Documents My music section. If not then delete it after you uninstall.
Re download I tunes. Maybe you got a glitch during the download. I am having no problems with ITunes and Windows 7.
You might want to disable your antivirus software before you do this so it will not have any chance of effecting the download and install of Itunes.