DVI-DVI-HDMI 3 montitor setup with a HD-5770. The 'HDMI' is a HDMI>DVI adapter. All 3 monitors are dell flat panels with signal entering through DVI ports. Will not allow desktop to be extended onto 'HDMI' monitor but windows shows it is there.
More aboutmonitor issue 5770 graphics card
your third monitor has to be hooked to a display port for it to work...