This was happening in the dream I woke up from this morning:

A shopkeeper had a pet dragon (looked like a half-length crocodile) and, though this was clearly a low-tech fantasy setting, loved to use Linux. But some software that he needed to run his shop was not available for Linux.

A destitute patron needed a favor from the shopkeeper, and had a magical scroll that would grant him one wish.

So the patron wished for a second dragon, that liked to use Windows, and gifted it to the shopkeeper.