You shouldn't need to buy a new motherboard. As reported, The BIOS CMOS data is corrupt. Your motherboard has ASUS CrashFree BIOS 3 which allows you to restore the BIOS if it becomes corrupt.
Download the latest BIOS version for your motherboard: http://dlsvr01.asus.com/pub/ASUS/mb/.../P5WDH2602.zip
. Extract the .ROM file from the .zip file and copy it to CD, floppy disk or USB flash drive, then turn on the computer with the media inserted, to recover the BIOS.
Page 87 of the ASUS P5W DH Deluxe Motherboard Manual
gives more detailed information on how to recover the BIOS.