From looking around, I have a feeling that you are correct that the setup.exe does not have a uninstall switch built in. It appears that the easiest way to silently remove the application and susequent files is to use the msiexec described in the link I posted earlier. I tried doing some more google searching and the program always came up.
As far as installing, it appears that you are doing everything correctly. I am working on and XP machine at them moment and it tells me that I need to use the control panel and not the Run command to install applications so I cant verify it but it appears that the install method is correct from what you described.
Kenny
Kenny