>>Right-click on desktop / personalize/displaychange display settings
>>
>>Your monitors should all be there with the Multiple displays options there. Some monitors specifics are down to the card i.e. sergey above
>
>The problem with that is that the 2nd monitor will only become visible in there once I plug the cable in the card. But, once I plug the cable in the card, the screen is blank.

But it sounds like it's more than just move to Win7. I had exactly when I replace an old monitor. The new one (which had defaulted) to primary monitor didn't like a frequency setting left by the old one. So the whole thing was blank. So I check the new monitors acceptable values (check the setting on another machine), replugged the old monitor, change the (monitor specific) refresh frequency setting (to suit the new screen - the old one didn't seem to mind). I then took it out and put the new monitor back on.