Starcraft and Dawn of War for RTSes. Now for some really dramatic, long lasting strategy games, Civilization IV, Galactic Civilizations II, and if you can get your hands on it Sid Meier's Alpha Centauri. I've also heard good things about Sword of the Stars, Crusader Kings (And the other three games in the series, Europa Universalis 2/3, Victoria, and Hearts of iron II), and Masters of Orion is considered one of the best 4X strategy games out there. (4X being games like the prior mentioned Civilization series, games about running massive organizations, usually countries, and leading them to some manner of domination over others.)
Dungeon Keeper 1 and 2 and Evil Genius are great for some odd toying around with strategy, in that you don't directly control your minions. For non-combat based strategy, SimCity, SimCity 2000, and Sim City 4 are all the good parts of the SimCity series though I imagine only SimCity 4 will work on Vista. But that's basically SimCity 2000 and then some so it's very good. SimAnt is also surprisingly enjoyable for being an ant simulator though good luck getting that working on Vista, and the original Railroad Tycoon and other similar business simulators require a great deal of thought and planning. The Movies is also a fun little game, with a machina aspect to it as well.
In fact one game, Capitalism II, is considered realistic enough that it was used to help train business professionals. But that again falls under the so old it may not work will with Vista.