Adanaxis won't work well with two monitors configured as a single display, as the place where all of the action is will lie on the join between the two monitors. When the two monitors are configured as two displays it should be fine, as it'll just use one.
Nevertheless you should be able to start the game using
which will start in windowed mode, and you should then be able to choose a fullscreen mode from the Options menu. I hope this works for you