cpu overheating

[The SHARK]

i own a system with pentium4 HT 3.00Ghz processor, intel 915GVWB motherboard.
From past 3 months my system displays a message:
" Previously your CPU was shutdown due to thermal event(over heating)".

it would work for half an hour or so and then shuts down(actually switches off).
when i start my system again i can hear some beep kinda sounds too.

i got my system serviced from many professionals.
after that it would work fine for 3 or 4 days.(only 3 or 4 days.)
now i hav changed my motherboard too.now i hav installed intel 946GZ motherboard.
still the problem persists.
PLZ HELP.
thank you in advance.

[shantanu]

Its not the Problem of your Motherboard, Do one thing,,, open your cabinet and see the CPU heatsink... its loose.. thats why its happening.. or try changing the heatsink... it wil work.. buy a new Intel heatsink it will cost you 350-500 MAXIMUM PRICING,, you can get even in 150 ok..

and then install it , if you cant install then take your system to the person you want to buy the heatsink from.. he will fix it,, your problem will be solved.. now go to your BIOS and to hardware monitoring incrase the CPU shutdown temp. by 5 +...means if its set to 50 then 55