Two Tone Beep from MSI 648 (MS-6585) Motherboard

Here's my configuration:

Raidmax Case with 350w Power Supply
MSI SiS 648 max/MS-6585 Revision v1.x, BIOS 1.3
Intel Celeron 2.0 Retail
2 Corsair 512MB 333 DDR Unbuffered DIMMs
Saphire ATI OEM 128MB Radeon 9000 AGP Card
80GB Hitachi/IBM Hard Drive
Windows XP

The problem is that the motherboard makes a two tone beeping sound
every 10~20 min according to pc-alert no noticeable rise in temp (34
degress is what it reads). Replaced Corsair RAM with Crucial Memory,
updated the Bios from 1.3, to the latest version from the MSI's
website, loaded the default BIOS settings, disassembled and
reassembled all connectors and parts, switched video cards, and still
the beeping occurs.

Has anyone experienced this problem or something similar to it, or
have any other suggestions?

Thanks.