The comment below by bionik sent me in the right direction.
bionik 71Posts August 18, 2010Registration date December 24, 2010Last seen Dec 19, 2010 3:01pm GMT
It's your freeware programs that detected iTunes like a potentially dangerous program and add it to their unwanted programs that's why you can't open it. You need to add itunes.exe to exclusions unwanted programs from your freeware programs.
I had recently acquired and ran Advanced SystemCare PRO v3. I just took the program off my computer, rebooted and the problem was solved.