Macrovision is a technology designed to prevent unlawful copying of copyright material from one source to another in laymans terms. Your graphics card has this built in (as do all) and it will only allow you to playback on your primary monitor, unfair as that sounds, as far as the MT (macrovision technology) is concerned you could be outputting that signal to a VCR, DVD recorder, projector which is interpreted as breaking copyright law.
It's an old technology that has never been 'hard to crack' but in terms of graphics cards they are very few 'fixes' about. (MT is built into things such as your VCR, DVD player and DVD recorder, Freeview box, etc) You basically stand very little chance of getting around it in terms of a pc dual monitor setup.
It seems a shame that when this technology is part and parcel of graphics cards that they don't include some kind of device recognition hardware, for example: playing back on a dual monitor setup = fine, playing back on a projector = a tad dubious, or even playing back to a DVD recorder = fat chance.