You can do this 2 ways. Run the emulator as an External Application or you can have it in the emulator section by adding as normal and setting Treat as 1 PC game to Yes. This would require you having one rom since like you said, it won't allow you to launch the emulator. So a dummy file would work fine. Can call it whatever you want. So your command should be: Fusion.exe In the Wait Before Keys section include: 1000 Which is telling it to wait 1 second before sending the keys. You might have to toy with this setting depending on your system. Then in the Keys To Send section include the following: ^b%{ENTER} What this is doing is telling GameEx to send Ctrl+B which boots the Sega CD and then Alt+Enter to send fullscreen.