Visual problems?

My computer no longer connects to my monitor. My monitor seems to be fine, working, etc, however it does not register with my computer as when they are connected and the CPU is in the monitor remains in standby no matter what I do.

Basically, I cannot get the screen to work. I have decided it is possible that my graphics card is not working? My fans seem to be running fine, and I can't see what else it could be... If anyone could advise me as to what could possibly be the problem, or how to solve it, it would be much appreciated. Oh and my computer is a Dell model.