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Wondering....When did you get that license file? Considering this: https://community.ptc.com/t5/Mathcad-Tips/Official-PTC-Mathcad-15-and-Prime-1-6-End-of-Sale-Announcement/ta-p/818870
But then, if you did recently get a license file for MathCad 14 for the given Volume ID, then you could change the volume ID of the harddisk to match the one in the license file. Try this: https://learn.microsoft.com/en-us/sysinternals/downloads/volumeid
Success!
Luc