found another working 775 mobo.
fixed the cpu in prob mobo to this working mobo and it is working - so cpu good
but tried other cpu on problem mobo - not working.
Well I tried something else too.
Powered up both mobo without cpu in socket. cpu fan just connected to mobo.
I observed the same scenarios with the same steps on both good mobo and bad mobo.
Hmmmm so more or less in bad mobo, when a working cpu is present even, it is as if no cpu!
Yeah this can be due to bad contacts in cpu socket and also I was not successful in cleaning properly.
Anyway to differentiate between bad cleaning and bad mobo ?
( Well may be nothing much can be done but good to know :-) )
Can take to a repair shop, but now no warranty so shop guy would be more interested in selling a new mobo