Its called SixtyForce
I personally use the 9.0 software because my friend gave me a code so its registered to me, I'll try to get him to get a code for it for all you guys.
All you do is download the version you want, drag it into your apps folder.
I suggest making a Games folder so you can keep yourself organized.
You need to open the application before you open the game.
Here's a site to download ROM's at-
http://www.coolrom.com/roms/n64/ (these are free but some are ESA protected so we can't download them :()
If anyones got more ROM download sites, please post.
Here are some I have
Smash Bro's - http://www.coolrom.com/roms/n64/1232/Super_Smash_Bros..php
Pokemon Stadium 2 (1 is on there too) - http://www.coolrom.com/roms/n64/1128/Pokemon_Stadium_2.php
I have a bunch more but you guys can find them yourself. (Diddy Kong Racing, Super Mario 64 etc.)
This is for mac, but I bet there's an emulator for PC.