And of course, a legal copy of the game you want to play. That's great if you want to buy a new copy of the game, but for people with an existing collection of games, an emulator is a better choice. You simply download the game and double click on it like any other Windows or Mac application. The games are all pretty reasonably priced (typically around $5 to $10) and there are regular sales and bundles on the site as well.
The easiest way to play an old game on your PC is to search for it on Good Old Games and buy it there. Whether you're an older gamer caught up in a wave of nostalgia, or someone who wants to experience the classic DOS games era for the first time, it's easier than ever to emulate the OS and play these games.