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 ? The talk will not provide definitive answers to the above questions but document some guidelines gathered so far from different perspectives: usage, architecture, exchange between emulated/physical word, open/closed approaches, community aspects... based on the speaker experience as user of emulators personally and at the NAM-IP computer museum but also as software engineer experienced in evaluting software maintainability, especially open source projects. It will be illustated on a practical case from the museum: the DAI "Imagination Machine" microcomputer. The ultimate long term goal could be to build a knowledge base shared across the community developping and using emulators.