+It won't come up ever. You click on itunes to bring it up and the licensing agreement breifly shows, and then goes away with out giving you the opportunity to click agree or disagree.+
Are you seeing similar symptoms when you try to launch your
QuickTime? (A brief flash of a screen and then nothing, no error messages?)
If so, check your PC for a Qoologic adware infestation. The free trial version of AVG Antispyware (formerly "Ewido") has been catching and killing that for most folks:
ewido anti-malware download