PC cannot boot up

I switch on my PC, there is no activity from the PC. Power lights is on, fan are spinning,hard disk activity light is always on, no display on the monitor, status light on the CD drive is always on.

Before this problem happen, I was scanning for viruses, it found 200+ viruses and removed most of it. I shut down the PC. When I switch it on, the problem as I describe above happen.

What is the issue here?

please advise

thanks and regards,