I'm not sure if Darwine works on PowerPC Macs, but I know that things like Bootcamp/Parallels/Fusion won't.

Assuming he has an Intel Mac, he could use any of these options. As for the lag issue, he may want to look into upgrading his RAM (not through Apple though because they seriously overcharge for the stuff). I know Apple was very into giving less than 2GB of RAM in almost all of the stuff pre latest release, and while the computers still function okay, eh, they could be better.