What to open game downloads with and how!?

[aceshebang]

I just downloaded the Sims and it worked, however, when i click on it on my desktop to open it, it reverts to this "Mail" thing.

I have to open it with something but I don't know how or what. Can someone enlighten me?

 

[Mackilroy]

What type of file is it? .dmg? .zip? something else?

 

[SHADO]

Yea telling us what type of file it is would be really helpful.