First and foremost if you can see an error code you Bios IS pretty much ok. It's when you get Xmas lights on the Eject button that you have toasted your bios.
Error 16 Means that the Box cannot find the dashboard files / dashboard files corrupted.
Error 6 means that the HDD cannot be unlocked, which I would expect if you just put the HDD in from another XBox.
Question is, before we proceed here, which Bios is in the Xbox with the problem? Is it an original or modded, if it's modded, then which one is it?
RE: Your own Xbox does that one have a modded bios (Reason for asking is that we may be able to hotswap and fix the troubled HDD with it if it's modded)
Regards,
Psi