When trying to open adobe

Question

when trying to open adobe reader 8.1.1 get following message: patch package could not be opened. verify that the patch package exists and that you can access it, or contact the application vendor to verify that this is a valid windows installer patch package. when we tried to install reader 9 got this message: could not uninstall version 8.1.1. tried to uninstall from the add/delete programs got the original message again. help please