Mac doesn't always read internal FAT32 hard drive

Hello! I have an early 2008 MacBook a1181 2.1ghz core 2 duo. A few months ago, I got an adapter to turn the optical drive into another hard drive slot. I put the hard drive that was in the regular hard drive space in the optical drive adapter. When I did this, it was in the format of Mac OS journaled with OS X Lion installed on it. When I put it I. The optical drive spot, I put an SSD in the original hard drive slot. I installed OS X LION on the SSD too. The SSD is my main boot drive. I then used the regular hard drive in the optical drive for media and different things. A few days ago, I decided to format the hard drive in the optical drive so I could use it as storage with Windows bootcamp too. When I formatted it, I formatted it into FAT32. Before this, it was formatted as Mac OS Journaled. When it was formatted in Mac OS Journaled, it always showed up on Finder under devices. Since the FAT32 format, it only shows up every once in a while. Sometimes I go into disk utility and it's there and I just mount it and it will then show up, but sometimes it does not even show up in finder at all. Why does it not always show up in Mac OS X Lion?