Western Digital WD Caviar Installation Manual page 46

Dual (Master) Drive: If you have a 2.5 GB or larger hard drive,
your system locks up on initial boot, and the drive you are
installing is the master drive in a two-drive system, set the
jumpers in these positions.
Dual (Slave) Drive: If you have a 2.5 GB or larger hard drive,
your system locks up on initial boot, and the drive you are
installing is the slave drive in a two-drive system, set the
jumpers in these positions.
42 Troubleshooting