Computer working fine but no image on monitor

Hello,

I have a Dell 3000 desk top computer. The computer boots up and shows a screen for 2 or 3 secs. It works fine behind the screen when I press the monitor on and off button and responds to moving the cursor blind. I can get on line and open files etc. But I am having to use the three second window to move around, including logging on and off. I have checked all the connections. I believe the original problem arose because I pressed the wrong buttons in a hurry. Is there some way the I can check if my monitor is gone before I buy a new one please? Would a new monitor not work because the problem is to do witeh computer commands please? The mouse is working as are the commands from the keyboard. Thanks in anticipation.