Many thanks Dominic
I did as uou suggested but the problem still there. So I think its the mobo.
Brougth it to the shop and they bring out the graphic card - still no display and they confidently said its the mobo.

As the mobo is AM2, its out of stock. MAny AM3s now they told me. I ran to many shops and luckily I got MSI NF725GTM - P31 (AM2).

The computer is ok now.