To get any of the "old" Blizzard games running on a "new" mac (i.e. any game older than WoW and any mac with osx), i would recommend the following (won't work with pirated games):
1. head over to:
www.battle.net (or directly to eu.battle.net or us.battle.net, depending on your region)
2. make a free battle.net account
3. select "add a game" in the "manage my games" section
4. enter the games serial number
5. click on "manage game" and select "download (pc or mac)client"
6. ???
7. Profit!
When installing any game downloaded from the battle.net make sure to use the new serial number shown on the website and not the old serial form the cd, the new serial numbers have 26 characters.
This procedure has several advantages over installing from disc. First you don't need the OSX Installer application, or rosetta, or updates/patches, or anything else. It just works! Second, you can download the game in a different language than the one you purchased (problably not relevant if your from the states, but here in Germany it's rather difficult to purchase english language games, but I hate german translations). And last, you can download the games to any of your computers, no matter where in the world you happen to be at the time you feel like playing.