Just because the origional drive was unlocked, does not mean it was formatted. Unlocking the drive and formatting the drive are two different things. Did anyone verify the drive was wiped before setting it up on their PC? It's possible the data was still there, just not accessable on the PC. It would then be wiped when the drive is partitioned and reformatted in the PC.
There is a possible scenerio here that makes it possible to do a drive swap without messing with the EEprom:
1) There is a possibility UTV only uses one password. That password is encoded when a drive that has never been in the UTV is inserted. This would explain why the drive is reformatted when put in the first time and reformatted if it has been reused in a PC.
2) Because there may be only one password, swapping drives that have been used only in a UTV may be possible. The only requirement is that the software be downloaded for each new drive.
3) If that is the case, once you have two or more drives set up, you should, in theory, be able to swap them as you wish without losing the data.
To test this, someone needs to record some programs, try doing the drive swap, record some programs, then swapping the orgional drive back in (without have done the trick of pulling the IDE cable) and see if the data is still there. Then try swapping back. If this scenerio holds, it should work. In this case, you could conceivably have unlimited drive storage.
Even if the drive is not immediately accessable and the software is downloaded again, it is possible the shows may still be there as the file partition may still be recognized and no formatting may take place. Until someone directly swaps the drive, then swaps it back there is no way to know for sure if swapping the EEprom is necessary. Pulling the IDE cable on the origional drive to unlock it may make the password unreadable by the UTV, which is why it can't just be put right back in and accessed. If someone does this and the software downloads again, check to be certain there are no shows on the drive before assuming the drive has been wiped.