You're totally right about the biometric part, it was obscure and totally lacked hints. It's very hard to get through without knowing the solution, since it doesn't make sense that renaming biodata.dll at the right time will allow you to bypass the security check.
The main idea was that the program checks the integrity of biodata.dll on launch, but not after that. I have seen lazy security measures doing just that in real programs.
Instead of renaming/moving/deleting the file after its integrity was checked, a more realistic approach would have been to replace the file with a cracked biodata.dll. It would make more sense.
But it was redundant with the first cracking conundrum. I ran out of ideas, had other things to do in the mean time, and totally forgot to improve this part of the game.