My Slave Drive is being used as a Master Boot Record so where are my files?

I formated my primary C: drive and partitioned it. When I up-graded to Window XP Professional I didn’t see my slave drive which was working fine before. It has 120 GB And I have about 111 GB left. It shows me that in the device manager box but it doesn’t have a drive letter. It won’t show up anywhere else in my computer except in the disk management but I can’t change or add a letter to the drive it’s shaded out.