Why is there a squealing screeching noise coming from my PC mother board?

I was given a used mother board and cpu a while back. The board is a Gigabyte model GA-MA74GM-S2 and all I know is the cpu is an AMDII and that the two worked in my nephews setup before he upgraded. I bought an Antec case with a EA-430D Green power supply, Corsair xms DDR2, WD Cavier B lue HDD, and Light On DVD RW. When I turn on the machine the cpu fan, case fan, DVD, and HDD power up but about the time the BIOS should come up I get an awfull screeching noise that sounds like an old dial up modem coming from the mother board. I presume it is coming from the mother board speaker but cant say for sure. It is not a fan, DVD, or HDD making noise for sure because I have disconected all those. The monitor stays in power save mode and I do not see any post screen or bios or anything. This not my first pc build but it is my first with used parts. What can make the mother bvoard speaker, if that is what it is, screech like that?