At http://www.gagaplay.com/jemu2 you will find JEmu2, which has always been a java based arcade emulator featuring online high scores.
Now I just added a driver for the MSX home computer, with support for PSG and SCC sound. If you click the link on the JEmu2 page 'Click here to start JEmu2 (MSX games)' you can play any of Konami's MegaROMs, such as Nemesis1/2/3, Salamander, F1 Spirit, Penguin Adventure and more.

If you could let me know if it works on your machine (Win/MAC/Linux, Java 1.4 or higher, OpenGL) that would be great
:-)

Cheers,
Erik