I am also facing the same problem with Internet Security 2009. I am using windows vista premium edition on my lappy. Some critical error forced me to use the system recovery manager and the settings changed to factory settings. Before doing the i have taken backup of whole system. I successfully recovered my system and updated the O.S to sp1.
Unistalled the Syamntec Antivirus which comes with vista using symatec tools. Tried to install the IS 2009 from my account but i am getting the error as "Installation Cannot Continue We're having trouble installing your McAfee software. Here are some things you can do to fix this:". I tried with MVT but that was not at all helpful. I used the MCPR tool also but still the same problem persists. Can any one throw some light.