For an IDE connection the last drive on the ribbon is the master. The one closet to the motherboard is the slave.
There are pins next to the moldex power connection. You will see a little plastic jumper on 2 of the pins. Or you may see 2 plastic jumpers. These can be arranged to the master/slave configuration.
Here is an illustration for Seagate drives.
http://www.seagate.com/images/support/en/us/u5_family_1.gif
Usually the drive itself will have an illustration on the sticker on the top denoting what the jumper settings are. If there is no mention on sticker, look on bottom of jumpers plastic encasement and you may see tiny little raised letters reading...
MS = Master
SL = Slave
CS = Cable Select
(if you are blind like me magnifying glass greatly aides this. :)
They are usually in the correct order as the physical connections. Most master/slave configurations are single jumper each. So if you have 2 on each drive, you can remove it.
**Oh Don't be surprised if you loose information as this will definitely change your master boot record.**
Save anything you want before trying this.
Hope this helps :)
Option number 2 would to get manufactures name off drive, visit their support website and seach for jumper configuration.