Play in windowed mode and stretch the window across both monitors. Most (if not all) full screen game modes won't span across multiple monitors (save for Eyefinity setups).
Thank you for your help. I guess ill stick with single monitor gaming for now. 2 gtx 260 sli still packs a punch for most games. Maybe upgrade next 2 series of cards. (ati 8000/ nvidia 700 series.