When you can build a PC (box only) for as little as $175 and less. Why would you pay $100 and and more for the OS? OSX $130, Cheapest Vista Ulitmate $180 (newegg).

When you can install Ubuntu (easiest install ever). Then get a three month subsciption with cedega ($15) and play your games just as you would on Windows. You don't even have to renew the subscription unless you want to update for a newly added\supported game. Cedega will keep running.

Hmmm $15 dollars vs $100 and more.