H/W or S/F problem

Hello chaps,

I had a computer but, now it is not working, I wish to know the cause for this problem and the solution to resolve this issue.

The problem in my computer is the monitor
seems to be switch off even its switch on [I checked the monitor cable connection its good & its led is also glowing]and while booting hard disk red light is not glowing. [actually i dont know whether its booting or not since I cant see anything on the monitor screen]

Please help me to resolve my problem.