Amerzone is an old favourite. When I got my first CD capable computer early in 2000, I bought four games at the same time: Myst, Gabriel Knight III, Amerzone and Pharaoh. This last proved to be a non-Adventure title, a sim which I found boring and never really played.
Amerzone is, as far as I know, the ONLY game in my collection of about 200 games to play on all the computers I have had over the time since I bought the game back in 2000. That's Windows 95, 98, XP and now Windows 7.
Amerzone's graphics (only occasionally slightly pixelated on modern machines), ease of control, and lack of game-stoppers like slider puzzles as well as its shortness make it ideal to sit back and play while winding down at the end of the day.
Since I do this every few weeks, I know the game by heart, and its a relaxing way to spend about an hour and a half. Playing at normal speed, I recently timed a playthrough at 1:22.