Software emulators are wonderful tools to study old computer systems for different purpose from running legacy application to retrogaming. This talk explores the context of digital preservation triggered by on-going work in a Belgian computer museum where emulators help in rediscovering old systems, maintaining/recovering knowledge on their design and sharing the experience with the audience without stressing fragile old machines. This talk aims at exploring and somehow engaging the audience about some simple questions from that perspective: where to look for emulators (MAME/MESS, specific development, javascript ports...) ? How to select one for some usage context ? And last but not least as emulators are themselves part of history: How to make sure/contribute to the sustainability of those nice piece of software on the long run ?