If you have connected your drive on the end of the IDE ribbon, the drive should be set to master.
If you connected the ribbon in between the first drive and the motherboard, the drive should be set to slave.
The configuration of pins can normally be found next to the pins (MS=Master, SL=Slave, CS=Cable Select), or on the front of the drive itself. The configuration of pins vary between drives, so it's important to check out what it says on the drive. For example:
