If you have Nero 9 you could try to use RescueAgent.
i always thought that once you removed the external HDD, it reset... once you place one into the PS3, it automatically wants to reformat it... i don't think you can swap HDD's and be fine...
USB hard drives are plug and play, they are designed to be removed. PS3s don't auto format.
maybe you put it in your computer and it did an automatic reformat...
Again, a pc won't automatically format a drive.
your computer can't read anything from the PS3 so, maybe that corrupted it when you plugged it into your computer...
PS3s can only read drives that are in FAT32 format, most PCs can read FAT32. If the HDD was in FAT32, there's no reason to think the files got corrupted, besides they would still be on the drive, just unusable.