My name is XXXXX XXXXX I'd like to help you with your iTunes problem. It sounds to me like your iTunes installation may be corrupt. What I'd like to have you try is downloading the newest version of iTunes and re-installing.
You may download iTunes from this link. http://www.apple.com/itunes/download/
Simply download it, and then run the installer. In addition sometimes these problems can be caused by not having the latest version of QuickTime installed so I'd also like you to download that as well and install it from this link http://www.apple.com/quicktime/download/
Try these 2 things and let me know how you make out. If you have any further questions don't hesitate to ask. And if this helps you out, please don't forget to click the green "Accept Answer" button so that I may be paid for my service. Thanks.