Motherboard speaker going crazy!

I have an older HP tower here, and the mobo speaker has gone bonko. It beeps once at power on as usual, then the HP logo/POST screen comes up, and the speaker start beeping really fast to where it sounds like a fax machine or dial-up internet connection. It does that for maybe 2-3 seconds, then it goes to a solid BEEEEEEEEEEP and does not stop until the PC is powered off. The PC won't boot past the HP logo, I can't get into BIOS; no keystrokes seem to work at all including CTRL+ALT+DEL. I tested the original CMOS battery and it was dead; installing a new battery had no effect. I have swapped out the CPU, PSU, RAM. I have disconnected the CD/DVD drives and the hard drive. I have removed all PCI cards. I even unlpugged the front panel audio, USB, LEDs, and switches from the mobo headers and that had no effect. So- obviously it looks to be a bad motherboard, but I'm wondering if there's possibly something I have overlooked.
Thanks!

 

What is the model # of the tower? It might be worth referencing the beep pattern against a manual (probably maintenance manual online) to see what it is suggesting the problem is.

 

@ collinsl: model is Pavilion a412n, and there is no real "pattern" to the beeping. Just a single beep right at the power on like a normal PC would do, then ultramegasuper-fast beeping for a couple secs, then a continous beep until the PC is powered off.

@ plodr: actually, it may be the keyboard controller on the motherboard 'cuz the PC was brought to me for repair for the reasons I listed above, meaning that it does the same things at his house with his keyboard. However, I will try it with a USB keyboard/mouse just to see if it makes a difference....

Thanks for the input folks! :-D

 

dlb,

OMG, Do you realize that may be the most acronyms EVER put into a single paragraph? :-D:-D

 

roflmao LOL roflmao LOL