Details can be found on this page, and you need to make sure you download both the Allied and Soviet disc. And while the game only officially supports Windows 95/95 and XP there is a handy guide for helping you to get it to run on Vista.
If after downloading and completing the first game you hunger for even more alternate history, you can head over to the EA Store and pre-order Red Alert 3 and then receive Red Alert 2 for free. You'll also get some swanky exclusive videos, and exclusive map, some wallpapers and a video of Gina Carano (schwing).
Red Alert 3 features three campaigns, each with their own story driven campaigns. Each campaign has co-op missions designed "solely around coordinating attacks and developing strategies with an ally". And if you don't have a friend to co-op with, you can team up with one of nine AI Commanders with different personalities and playstyles to complete the game!