Hi there Ive recently brought and installed a GTX770 and am running my GTX295 as my physx card which works but is using only half the card, so is there a way to make it use both sides? as in both gpu's on the 295
If the 295 is a dual gpu card on a single board then only one of the gpu's on the 295 can be used. You can add an additional card for separate PhysX support. DABhand is plain wrong in his response. But only 1 gpu can be relegated to that duty from that card.
Frankly you can't really utilize your 295 to it's fullest potential as a secondary card. You could reverse their roles but I would suggest against it.
I would suggest selling the 295 for extra cash. You do not truly need it with the 770 unless you run PhysX games at both 2560 and High PhysX setting. If you run at 1080P the card is more than powerful enough for both duties.