You can buy old PC games (generally dating from the early 90s to early 2000s) for prices generally ranging from $5-$10. The games are completely DRM free (you can install them on as many PCs as you want, and you can re-download them without having to pay again), and optimized to run on Windows XP and Vista.
When you buy the game, you can also download high-quality PDF files of all the manuals and documentation, artwork, and the game's soundtrack.
I bought Fallout (a game I missed out on) a few days ago, and am really enjoying it.
A legal and cheap way to enjoy the golden age of PC gaming once again. Also, your (my) crappy computer can probably run most of them.