Master slave

if you r having 2 hard disk read the instruction given on the top of the hard disk because the jumpher setting for different hard disk may be different.so make one hard disk master with slave by putting the jumpher(connector of two pins)in appropriate no pin pair and make another slave connect the two hard disks with the IDE cable(do it after turning off your computer).after then start your computer for clarification check your BIOS setting whether whatever you have don is right or not.in BIOS main section the information about master and slave is given

The previous post provides the correct answer
Check the vendor's manual as how to change the jumper.
For making the Hard disk master and slave the change of jumper position is a must.

Vinay is right.