_______________________________________________________________
Why won't my two IDE drives work together?
Assuming that the drives are attached to the same controller and they
work properly when attached one-at-a-time, you probably don't have
them configured properly for Master/Slave operation.
When operating 2 IDE drives, one must be designated as "Master" and
the other as "Slave." There are jumpers on every IDE drive to
configure this. Check your hard drive manuals for the jumper settings
for your drives. In general, it doesn't matter which is which - just
pick one as master, and make the other slave.
In your CMOS configuration, Drive 1 should have the parameters (heads,
cylinders, etc.) that match the drive you set as "Master" and Drive
2's parameters should match those of the "slave" drive. In operation,
the Master will appear as drive C: and the slave as drive D:.
Because not all hard drive manufacturers follow the IDE specifications
closely enough, drives from 2 different manufacturers may not work well
together. In this case, changing master -> slave and slave -> master
(along with the appropriate CMOS changes) may help. If it doesn't,
then trying two drives from the SAME manufacturer is the only avenue
you have left.