GOG's preservation program is a commitment by the distribution service to ensure that classic PC games included in the program will run on your Windows machine no matter what. This doesn't mean included games will receive any fancy overhauls or resolution boosts—quite the opposite. GOG's pledge is to preserve the look and feel of the original experience, while ensuring the games boot without any intervention from you.
GOG launched the program just under a year ago, with 100 games such as Dungeon Keeper, Theme Hospital and Blade Runner receiving the badge of +1 compatibility. As of now, that number has increased to 250.
