While it may not be your thing, I've been intermittently playing The Battle for Wesnoth, which is a free turn-based stratgy (ie fantasy war) game. Nicely designed and balanced. not flashy on graphics, so it's pretty forgiving processor wise, and written for most operating systems (I know it's Mac and Linux compatible; dunno which PC OS it's friendly to). Based around campaigns and unit advancement, so you do develop favourite units etc.