If your drives are connected on the same cable, and one is a ATA100 and the other is an ATA133, the faster will default to the slower speed.
Also, you may want to check to see how the jumpers are set. Sometimes default is set to cable select, and this can cause problems if the other is set to just master.
Also, if your running an 80 pin cable, your "master" drive needs to be on the end of the cable, not in the middle like under 40 pin cables. It may be trying to detect the drive if its in the middle during boot.
If at all possible, you should always run a slave drive off the secondary channel, not with the master. You'll get much better performance that way.
