How to fix iTunes install failure on Windows 7?

Current ITunes user on Windows 7 & app working fine. Dialog box pops up stating update to install. Proceeded but install failed with suggestion to download update. Down loaded off Apple web site. During installation got message activating mobile devices failed even when user had administrative privileges. I chose ignore. When I ran new iTunes install got "Program can't start because MSVCR80.dll is missing..." Tried reinstall. Same problem.

Suggestions?