To install the utility, doubleclick the msicuu2.exe file you downloaded.
Now run the utility ("Start > All Programs > Windows Install Clean Up"). In the list of programs that appears in CleanUp, select any Bonjour entries and click "Remove", as per the following screenshot:
Quit out of CleanUp, restart the PC and try another iTunes (and/or QuickTime Player) install. Does it (or they) go through this time?