Acrobat 9 Standard

I am using Acrobat 9 Standard on a Windows 7 professional computer.  I get messages that prompt me to check for upgrades for Acrobat.  I try to upgrade but I get an error message that says an upgrade patch cannot be installed by the windows installer service because the program to be upgraded may be missing or the upgrade patch may update a different version of the program.  It asks me to verify that the program exists on the computer and that i have the correct upgrade patch.