I am presuming u are using windows 95/98. You must go to the control panel choose the system tab. then go the device manager which is the second tab after u double click on system. There under hard disk controller u will have the bus master ide controller for your hard disk change the settings for that from default to both channels enabled(this will enable both the primary and secondary channel after which both your hard drives will work.).
I have this old Pentium 2 pc w/ 2gb hard drive that is 99.9% full (Maxtor). So I took a secondary Harddrive from another computer (2gb Quantum Bigfoot) and installed in computer and set it as the slave. Upon booting up, both hard drives show up on start up window. But when I go to explorer or try to find or access the 2nd drive, I cannot locate it. I thought it would automatically assign it to D: but my CD is currently given that drive. All I see is the original C: that is just about maxed out. Do I need a driver or something? Is it just not compatible? Thanks in Advance