No idea why it would not install. You should be able to install almost on any machine, it is activation which is the issue (only two machines allowed).
All you are getting is the Bridge module. I would suggest running a deinstallation on Elements 5 first (not a manual removal) and, if you have for any reason previously installed a trial or beta copy of CS3, you MUST run a deinstall on that and clean out ALL files associated with it. This is a big problem. I ended up buying a new machine to install CS3 on Mac, the trial version has totally screwed up my previous one for a reliable installation, without wiping the HD.