Sounds like the previous owner installed some modded fw for their own use and then sold it on with that on the drive. You should, depending on the fw installed be able to go back the manufacturers fw tho, sometimes the fw update program doesn't recognise the drive because of the modded fw but until you give it a go you won't know. Worst that will happen is that it just won't update the fw, the drive will be ok as long as you follow the normal precautions. If you're not sure what to do there is a link in my signature to a mini fw update guide posted by Shamus, take a look at that