Laptop's Display Goes off but the system is running

[Archer_25]

Hello,
My laptop's display goes off frequently every 10-20 minutes. I tried to connect my laptop to CRT external monitor but it also has a same problem, both display's are not working.I contacted Dell Support their engineer replaced my LCD then he re fixed my motherboard and heat sink then laptop started working for at least for 45 min's and then it goes off again Please Help !!!!!
My system Specs are:
Intel i5-450M GHz
4 GB DDR3 Ram
ATI radeon 4650 1 GB graphics card
320 GB hard drive
Windows 7 64 bit

 

[king smp]

This might sound silly but did you check your power settings under the control
panel
just make sure that the computer is not being put to sleep
sometimes with some laptops they will not come out of sleep mode
try turning it off to see if that helps

 

[Archer_25]

no it'snot in sleep mode

 

[plasmastorm]

Try updating the driver. A lot of Nvidia cards had issues similar to this under win Vista.

 

[Archer_25]

I have updated it to latest graphics drivers supplied by ati Catalyst 11.b +hot fix