Strange, Random, high pitched system beep even when unplugged

[malibu35072]

I need help here as this is driving me insane.

I have a system with

Gigabyte ma770-ud3 rev 1.0
Phenom II 1075T six core CPU
Gskill DDR2 1066 4GB dual channel
Cosair 650W PSU
old MSI CDRW
Sony Optiarc DVDRW
3 WD caviar HDD SATA
EVGA GTX 275
Dual Monitor configurationg
USB keyboard and mouse
Using onboard audio. Speaker out, Mic in, and aux in ports used.

Ok so the problem is I'm experiencing a loud beeping sound at any point in time, during any state the system is in.
Again this is NOT during POST. There is one single lower pitched beep during POST, that means everything is ok.
The sound specifically is a very high pitched tone, lasting about 1/2-1 second appearing no more than one "beep" every 10 minutes but otherwise random. It seems to be coming from the direction of the PC tower. The tone will sound no matter what state the computer is in, including running windows, running memtest, sleep mode, powered off, and EVEN with the power supply AC main unplugged from the back of the case.

I've inspected the system visually, everything appears in good order.
I've cleaned all dust from the system.
I've checked system temps in a monitor AND in BIOS, all are under 50 C, Video card too is acceptable ranges.
I turned off all fan and hardware alert tones in BIOS
Stress tested with prime95, furmark and a WMP playing mp3 tracks simultaneously, no problems.
Ran Memtest.
POST video feedback mentions no errors.
HDD SMART reporting reports all HDD drives in good health.

So I have no idea whats going on, and sadly I do not have spare hardware to swap in and out.
I have suspicion of the CMOS battery, but I'm not aware any messages regarding it.

Any help here guys. I'm dirt poor (yay recession + student loans) and cannot afford to just go on a part spending spree. I want to find the part causing this problem and deal with it.

 

[inzone]

Well , you could remove the cmos battery and see if it still does it because with the psu unplugged that is the only source of power you have in the computer.

 

[FinneousPJ]

Yes I'd guess it's a warning your CMOS battery might be dying.

 

[malibu35072]

I replaced the CMOS Battery and I still have the beeping sound. I also noticed a very low volume high pitched tone playing though the system speaker continually when I turn the power supply on but the system is still in "shutdown/standby." Its very faint, as I can just barely hear it.

I unplugged everything but the bare minimum of stuff I need to make the system run. Mobo, CPU, my main boot drive, memory, and GPU.

I've been testing memory sticks independently in memtest, no errors reported.

What should I do now?

 

[malibu35072]

Bumping with a new Update:

I've unplugged the case speaker from the motherbord and I still hear the beeping sound.

I now suspect my power supply. I have specifically a Corsair CMPSU-650TX 650W. Do those have their own speakers for error codes? Large capacitors might explain why it beeps even after being turned off.

Also does the video card emit a beep?

 

[rb420]

Did you check your microwave? You dinner might be done....

NO but seriously, that is weird. Hope you figure it out.

 

[JinxM]

Are you sure it's not a roommate pulling a prank?
http://www.thinkgeek.com/gadgets/electronic/8c52/?cpg=cj&ref=&CJURL=&CJID=721540

 

[JinxM]

Are you sure it's not a roommate pulling a prank?
http://www.thinkgeek.com/gadgets/electronic/8c52/?cpg=cj&ref=&CJURL=&CJID=721540

 

[hat1324]

Very sorry, I know this is a very old topic, but I have yet to find an answer to this problem anywhere. The beeping is (was) your monitor I think, I just had that same problem...