Dan,

(1)
you speak of "Microsoft Entourage" you try to dl.
But you also speak of my original entourage mail manager ?
What do you mean by this term ?

(2) It is very difficult to give a general way-of-working to install an application -you've downloaded from the p2p. Most of the time:
(*) they came as an archive you have first to unzip.
(*) then, most often, you have an "image" (.dmg) you have to double-clikc on to mount on desktop.
(*) inside this mounted image, you either find the application or an installer.
(*) the installer has to be runned to obtain the final application
(*) when the application is launched, a serial is generally required to go further.

My personal opinion is taht I do no trust at all to downloaded applications from the p2p; they can be fake, contain viruses or be incomplete so that their installation may harm the system

Phil

By the way, could you detail your machine and OS