I finally got it started after more than a week. I found, on this forum, the following:
I have come across several people who have had iTunes fail to start up in the past few days, all with v.9
Ok, from what I have seen in other posts the problem seems to be related to the Bonjour service which is the program mDNSResponder.exe
After you have tried to start iTunes, Right-click on the Taskbar -> select Start Task Manager -> Processes Tab -> select Show Processes from all users -> select mDNSResponder.exe in the list and then click End Process
iTunes should start, if it doesn't end the iTunes.exe process in the same way and try launching iTunes again.
If you do get iTunes to start then we can permanently solve the issue by disabling the Bonjour Service.
START -> Run -> type services.msc -> select Bonjour Service -> right-click, select Properties -> in the dropdown box for Startup Type select Disabled