Laptop Ringing Noise, no other sound

Hi guys, as the title states I have a laptop that has dropped all other noise for a continuous ringing noise. It's about the same tone and pitch as the Emergency Broadcast System's test, but without the modulation. No other sounds come out of the speakers and the sound even emits when muted. Plug in headphones and you get that noise from the headphones, but still no other sounds.

Things I've tried so far:
Roll back the driver for the speakers/audio
Update the driver for the speakers/audio
Revert to a previous restore point before the noise started
Disable speakers
Uninstall speakers

Nothing makes any difference. Any ideas?
Dan

 

Thanks for the reply. Sorry, I should have said it's my wife's HP G60 519WM.
http://h10025.www1.hp.com/ewfrf/wc/product?cc=us&lc=en&dlc=en&product=4039377
Windows 7-64
3gb of RAM

I looked in the BIOS (Esc key at startup) and didn't see anything that can be changed to do with much of anything. There was a diagnostics section but that was Memory and HDD. There was also a log but it was empty. I can change the bootup order and the clock and that's about all that's there. I looked on HP's site and there was a driver for the audio. I downloaded that and installed it in case my driver is defective but no change.

Any other suggestions?
Thanks
Dan

 

Thanks for the suggestion. I tried cleaning the keyboard, checked all the keys. None that appear the least bit stuck. This is my wife's laptop and she takes much better care of her stuff than I take care of mine. :-D I even went so far as to uninstall the keyboard and the problem persisted. I suspect this is a hardware issue.