I recently updated to windows vista

I recently updated to windows vista, and 7. I had the same problem with both OS's. Whenever i try to install certain programs i get a message that says..
"This installation package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid windows installer package."

I have tried manually updating windows installer, but i cant seem to figure out how to fix this one. Currently im running windows 7 64 bit if that helps.

Thank you,
`Stryffe