[Crombeen]

That machine isn't too slow at all, it can still do solid work at that machine.

I've got a very very first Generation of the MacBook Air 1.6 GHz 2GB RAM and can still load this game but heavy.

So I guess to run this game on a Mac and compared to the min. Windows specs you'll need at least a Core To Duo processor of course ( better known as an Intel Mac ) 2.0+ GHz processor speed and 2GB RAM.
That's almost any iMac or MacBook from Late 2006 or Mid 2007 or younger.