Compaq laptop will not boot?

Hello,

My compaq laptop will not boot up after I turned it off while it was installing a update. When I go to turn it back on I press the power on button then it acts like it is going to boot when after only a second or two it go click and shut off then click and try to boot and then click off and then click on again and do this over and over and over. The screen never comes on so I cannot even get to the point where I can even try to get it up in safe mode..... I have not had any problems before until this happened to me. I did get it to stay powered on (No screen though) by holding down the ctrl key and alt while turning it on. It stopped going on and off rapidly and seemed to stay powered up but still not booting? I have been around computers for a long time now and this is the first time I have ever seen this happen.