Brysonblack
What do the data cables look like? If they are ribbon cables with 40 pins, then these are IDE drives and master / slave applies. If they are the narrower cables with seven pins, then these are SATA drives and master / slave does not apply.
Whoops. Quantum fireball. That's old, and an IDE drive indeed. So. Each IDE cable can connect to two IDE drives. One of them, or the only one, must have the jumpers set to "Master." The other, if you connect two drives to the same cable, must be set up as the "Slave."
Jumpers are tiny fiddly little connectors that will short out a pair of pins on the back of the drive; I always use needle-nose pliers to handle them.
Here's a picture of someone with fingers smaller than mine installing a jumper:
http://www.pcstats.com/articleview.cfm?articleid=1778&page=4 . Not that this particular drive has the pin assignments neatly printed on the circuit board by the pairs of pins.
Is your current boot drive an IDE drive also? Can you tell us what model motherboard you have, or at least how many IDE connectors it has? What version of the OS are you running?
Finally, are you familiar with the BIOS menus, which can make the troubleshooting a little easier for us?
(Please note that the names Master and Slave may not be used in California, where the drives must be referred to as Primary and Secondary, pursuant to state low 143.23.a)