From now until Tuesday, November 27th, Phantasy Star II, III, and IV are available for a reduced price as part of the autumn Steam sale. They're $1.49 individual or $3.75 for all three and some other Sega Genesis games in a Classics pack:
http://store.steampowered.com/sub/14445/
This is a great time to buy them, if you're looking for a new way to play these classic games on PC.