If you don't know what Fat32 is, it'll be extremely hard to explain it to you. Its basically the format that your HDD uses for storing files, etc. All HDD use these types of formats. Fat32 is the oldschool format that was used on pretty much ever HDD before 2000. It only allows for a maximum single file size of 4Gb, which Sony made the requirement for externals to prevent piracy of games. So no individual file under Fat32 can be more than 4Gb. You can have 1000 different 4Gb files, but nothing more.
Plug the external into your PC, backup any files you've already gotten saved on it to your PC, and then open up disk management and format your external to Fat32. If you're on a newer PC you'll have to download a tool to do it since they no longer have the option for format under Fat32. Then copy everything you have back over onto your external drive and plug it back into your PS3.
