The problem is nVidia. It only supports dual monitor output, despite the three connectors. Only two can be active at the same time. There are a few options:
1. Get another nVidia card that uses the same driver and use that one for the third display. Check carefully whether your PSU can handle that.
2. Get a Matrox card, but that often goes with other problems, because their drivers are always out-of-date. Matrox stuff is best used for its designed purpose, as a doorstop. (When CS6 comes out, all Matrox stuff will be outdated and require a new card, but you have to wait at least 6 months for a stable driver version, IMO).
3. Use the Scart cable to connect to a DV deck and output to an external device (only in SD format) over firewire to the deck and then over Scart to the TV.
Unfortunately my Sony tape decks firewire connection has stopped working so I suppose that rules that out. Ok is the Matrox card my only option or can you recommend a cheaper brand to get around my problem?
BM Intensity or AJA are alternatives. I still use option 3 but plan to go to option 1 in the near future.
Will the BM Intensity Pro be a good option?
And is it easy to use?
I Have just found this card similar to the Intensity.
Would you happen to know if this will work for my purpose?
Yes, Blackmagic Intensity Pro is a very good solution to preview HD on your LED LCD. And it's not expensive.
Harm is right, forget the Matrox. Any Matrox!
Thanks for your help guys.
Tomorrow I will get an intensity pro.
Your advice has been much appreciated!!
All the best.