Thanks turingtest2 and nice handle name. I had this problem regarding MSVCR80.dll.
My system: I have a Dell desktop running Vista. iTunes would not work and reinstalling did not work.
What worked was uninstalling most of the apple software as described above by turingtest2 and then reinstalling itunes as an administrator.
What I uninstalled:
iTunes, Apple Application Support, Apple Mobile Device Support, and Apple Software Update. Bonjour and iCloud
I did not remove all Apple publisher programs: eg, Quicktime; VoiceOver Kit.
After that: I rebooted the computer (Windows Restart); downloaded iTunes; and installed it.
It worked.
All of the above, plus googling to find out about MSVCR80.dll, took a lot of time and was quite a hassle. If my wife or kids had to do this, it would be challenging. It seems this all happened after an iTunes update. Apple, please be careful with your updates and releases!