Macintosh????
I looked high and low for a Mac sim, but could not find one. I ended up getting the Real Flight to run on my girlfriends PC.
Depending on your finances, it may be worth buying a separate PC. Find a cheap PII or something. I've noticed a big improvement in my flying thanks to the sim. I consider myself a beginner, so if you're experienced, I'm not sure it'd be worth buying another computer.
Mike