I have newly installed

intel duo core processor 3 GHZ with intel 945 GCNL motherboard. I assemble every thing. But when I turn the cpu on. It automatically turns off after about 5 seconds.

When I reboot, I hear a siren beeping two TIMES and then the cpu turns off.

I have only one heatsink and fan( that comes with the processor) and is working properly.

Do ANYONE help me please. I don't know what to do.

I shall be very very thankful.Disassemble everything so that the only things connected to the motherboard are the:
cpu / cpu fan / RAM / power SUPPLY. Reseat the cpu/RAM &b power supply connections. Boot and see what happens.

If it still does the same thing, remove the motherboard from the case / reconnect as above and TRY again.

If that still doesn't work you have a BAD cpu/RAM/power supply/motherboard.

Alan <>< Do you follow correct procedure in applying thermal paste to the processor before mounting the heatsink on it?how can i apply thermal paste, do i have to buy it separately because paste is not given with the processor.

and processor book also haven't mention anything about it
Did you buy the heatsink and fan separately? Did the heatsink have a thermal pad on it? Did installation instructions come with the heatsink?

See Installing a CPU and Heatsink

yes sir,

the processor came in a sealed packet with heat sink and fan, heat sink and fan are of new round shape.

There is only a intel book which have not mention of thermal paste. do it come separately.

A slight paste in there on the top of the processor and lower part of the heat sink. but it is not enough i think only slight paste.The language translation is a bit difficult to understand and I'm not quite sure exactly what you've done during the process of assembling your computer.

So, I think you should carefully read How To Correctly Apply Thermal Grease, remove your heatsink, clean the old thermal compound off of it, and apply new thermal paste/grease as explained in the article.