Win ’98 will not recognize 2nd harddrive

I had 2 harddrives in my machine. The 2.1 gig was the master and the 1.6 gig was the slave. I swapped out the slave for a 10 gig. The bios recognizes it and it is even showing up in device manager. But, a drive letter was not assigned, so I can’t use it. This is a used drive w/win 98 on it. What can I do to resolve the problem?