Help with installing dual monitors

I've recently purchased another monitor to use on my computer. I want to use this primarily for my work with Photoshop. Can anyone tell me how to figure out if the original video adapter on my computer is capable of supporting dual monitors? I know that once I connect the monitor and the computer detects the new hardware, it should be simple enough by checking my display settings. If I don't have the option "Extend my Windows desktop onto this monitor", its obvious that my video adapter doesn't support multiple monitors. But, is there a way to tell in advance?

Any help would be appreciated.

Debbie