black screen on laptop & external monitor

Hello,
My HP pavillion xh365 laptop has developed a problem with the screen going black. This happens after running for a few minutes to several hours. The screen goes completly black with no faint outlines showing. I have tried running the onboard diognostics, but get the same trouble. The only way to recover the screen is to reboot. I have the same problem whether the laptop is running on the built in display or is conneceted to an external display. Both screens go black at the same time. When the screen goes black, I can hear some changes in the pc. The sounds I normally hear are just the hardrive and the fans, but when the screen goes black, I hear some changes in the pitch of one of the sounds.

I have not recently made any changes to the system.

What do you suppose is causing the black screen?

Thanks to all, Jerry.

 

Hardware could be failing; my advice is to use a program like SIW or if your BIOS supports it to check the temperature that your laptop is running at. The increase in noise could be related to the pc unable to vent properly. The excess heat would cause problems. Also, have you tried a system restore or rolling back your video driver? :major

 

Here is the link to download new drivers. Don't know your OS so you will have to put that in:cool. HP Pavilion XH365