I released my ZX Spectrum emulation Wspecem, and GPL sources first time publicly in the Internet at large, the 15th May 1996, for Windows 95.
I am quite sure it was the first ZX Spectrum emulation developed specifically for the Microsoft Windows 3.11/95 API - (or any previous Windows versions before that)
Can I claim at least, it was the first ever non-commercial computer emulator developed for Windows? At least at the time, I did not find anything else.