Just as "anchor":
Officially, the last stable release supporting XP was
v0.70.2...
There was a
link to Aleksoid1978's diff to 0.70.2.1 with experimental CUVID H.265 10-bit decoding.
And clsid published
MPC-HC 1.7.13.1 incl. a patched LAV Filters 0.70.2.3.
From there, the thread kept derailing over and over.