advise on multiple displays

[mercmanuk]

driving me mad.
on my pc ive an onboard graphics with a hdmi and a dvi inputs,i also run a better quality graphics card with dual dvi inputs.i run two 24" monitors on the additional card in extended mode and they work fine.
ive just wired my 47" led tv with a hdmi cable to the pc which I connect to the hdmi input of the onboard graphics.
with the tv amp off the two monitors are displayed as 1 and 2 then with the tv amp on the tv shows as 3 in the settings.
sometimes with the tv on the pc desktop in displayed on the tv but the mouse curser wont move onto the screen it moves over screen 1 and 2 but not 3.
hope ive explained without going on but its driving me mad.
want to be able to watch films on the tv streamed from the pc or net.

 

[mercmanuk]

after some research on the net I might be better going for a graphics card that supports 3 monitors at the same time,most do hdmi/dvi and vga but only a choice of two at any given time.