How To Fix a Computer That Turns On But Displays Nothing

I've got a problem with my monitor/display and I hope it's not a sign of the mobo going bad. My computer all of a sudden decided to freeze up, and upon restart, the monitor won't get a signal, the light stays yellow. All the other components appear to be running fine, all fans spin, and the HDD appears to be running, there's just no display going to the monitor. I've tried two monitors on it and two different vid cards, I've unplugged and rearranged the RAM, and still nothing. Also, for some reason, when it starts up, theDVD drive keeps acting like it wants to spin, and just keeps clicking away. I'm completely stumped, and hopefully this isn't a sign of the mobo going bad. Any help would be great appreciated!