Why is there no longer a signal to my monitor?

When I shut down my PC yesterday Windows XP Pro had updates that needed to be installed. After installing the 6 updates the computer shut down normally. When I went to start the computer a few hours later my monitor is saying it’s not getting a signal. I tested the monitor on 2 other computers and it works just fine. I’m out of ideas as to what the problem is. It was working just fine untilthen.