You might be missing the video codec the 360 videos need. XP wasn't developed when stuff like that was a thing so it might not be included.
lando242,
You are right. On the html5 / multimedia / video test I have 4 things missed on 35: Audio and Video track selection, MPEG-4 ASP support and H.264 support. So this is a local problem. Not related with Opera. Thanks for your help.