Not to be a dick, but it's only really worth mining with the ATI cards. Additionally, you should be able to point a different instance of CG miner (or any other miner) at a specific GPU.
Your wrong, usually you need 1 instance of CGMiner.
I know, I was providing an alternate method to use all of his GPUs, even if a single instance of CG miner cannot detect all of them. He should be able to see if the 460 is detected by running poclbm.py with no additional parameters. If it was still failing to see all of them and he was using Linux I'd try setting export DISPLAY=:0