I'm running a 430 GT, and I have two monitors, an HP 2007w @ 1680 x 1050, and an LG TV on RBG mode with 1440.
When I started using dual monitors, I could run World of Warcraft on my main screen and watch a maximized Youtube video on the other screen while World of Warcraft was set to Fullscreen on the main screen. Now, when I try to do this, it turns off the other monitor and blacks it out while in Fullscreen, and only works in Fullscreen Windowed now. I never ran it on Windowed because my FPS dropped severely.
How can I get the second monitor to display the video while in Fullscreen mode? I know 100% that I've done this, and maybe I changed a setting and didn't remember. I don't think I did though.
you probabily updated your driver. companies often break features in updates. for example, currently i cant save my multi monitor profiles for fast switching between them.
check for a new version, maybe they fixed it. or you could always try an old one.
You couldn't do it in purely fullscreen mode, due to it's nature. However, it's possible to do it in Windowed fullscreen mode. It acts as windowed in multi monitor situations, but looks like fullscreen. Give it a try!