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@righto123 I'm not sure, but it could be videomode related, see if that helps: https://wiki.recalbox.com/en/tutorials/video/display-configuration/complete-video-configuration-guide
Have you already tested it with another TV to see if it influences?
@Righto123 What I do know is that Dreamcast requires "OpenGL> = 3.1 GPU" to work on the PC: https://github.com/recalbox/recalbox-os/wiki/Board-Compatibility-(EN)
None of the Dreamcast games are running on the PC, or just Marvel vs. Capcom 2?
If none works, it is the video card that does not support, if it is just one game, try changing the emulator / core.
