mmmm, Initalizing...
Western Digital Caviar SE 120GB 8mb cache run in 7,200rpm... Check.
ASUS A7V600-X... Check.
mmm... I am not sure but DID you check THE PLUG??
suggestion
A:\ Floppy drive
C:\ Old IBM in IDE1 set in MASTER (Should be plugged in end of the cable first)
D:\ WDC HDD in IDE1 set in SLAVE (should be plugged in second from the end of the cable)
E:\ CDROM/RW/DVDROM/RW In IDE2 set in Master
F:\ CDROM/RW/DVDROM/RW in IDE2 set in Slave
Be aware, i have heard the rumours around techspot that SATA wont work with EIDE cables. I have tried the remedy with my Seagate Baccauda 7200.7 ST380013AS in RAID 1 (striping) and Maxtor DiamondMax Plus 8 9.45gb. Alas, it work but Bios reconized my maxtor and boot out my seagate.
Why not you try to run your WDC first in bios to see if it work. If it work, try run both in separate IDE (IBM in IDE1 and WDC in IDE2) If it works too, try to put both hdd together IBM in master and WDC in slave. if it work, here you go, if not work, go to previous step and use that configuration.
Lucan
P.S. Welcome to Techspot.com!