What is the high pitched beep from my Toshiba Sattelite A105?

[Aimee Dutton]

This happens rarely but shortly after this happens I experience issues, slowing down of the computer and specific websites like Facebook. Any help is greatly appreciated!!
Have run a virus scan, malware scan, adware, spyware, etc. All has been cleaned and nothing found now but still not working properly.
Not on battery, has not been run on battery alone for quite some time.

[Jay B]

may be low battery. or virus. scan your computer.

[Renee H]

I had one and it meant low battery. It got on my nerves