Dreamcast-Talk.com

NullDC is a popular emulator for playing Sega Dreamcast games on your PC. While it's known to work well on older versions of Windows, like Windows 7, there can be compatibility issues when trying to run it on Windows 11. Some users have reported success using compatibility mode or tweaking certain settings, but it's not guaranteed to work smoothly. In my opinion, if you're really keen on using NullDC and it's not working on Windows 11, you might want to consider dual-booting with an older version of Windows or exploring other Dreamcast emulators that are more compatible with Windows 11.

Just use Flycast on PC, it's better.