|look in the device manager, and see if your graphics card is listed twice, it means it has 2 GPUs.|
This is an important distinction: something like a Y splitter will allow you to send a single screen image to 2 monitors instead of just one. But the images are clones - it's the same desktop twice. This can be accomplished using any graphics card, a Y splitter, and 2 monitors.
only with 2 GPUs will you be able to run 2 monitors AS ONE, which i assume is what you were hoping to do. Please note, 2 GPUs does not mean 2 graphics cards (SLI/Crossfire), it just means your graphics card has 2 processors instead of 1.
in either case, the monitors don't need to match. you just need to have the appropriate DVI and/or VGA cables and adapters. But you could hook up a 22"LCD to work side by side with a 15" CRT, it'd make no difference to the OS.