I'd try cleaning it off completely and starting fresh. Install in the desktop unit and go to Disk Manager. First step will be to right-click on that unit and Delete all Partitions it may have. When you're back to nothing but Unallocated Space, Create the Primary Partition (maybe this will be the only Partition, using all of the disk space), and make it NOT bootable since you plan is to use it for data only on a PS3. Then Format it using the FAT32 File system.