It's more common than you would think...
You have to confirm your password when installing so the chances of it being typed wrong both times are slim but not impossible, maybe that's it.
The OS might be 700mb on disk but that could be up to 2gb when installed, keep that in mind. I wouldn't bother with an extensive write-to-zero, it should make absolutely no difference.
Have you thought of using virtual machines?
You have to confirm your password when installing so the chances of it being typed wrong both times are slim but not impossible, maybe that's it.
The OS might be 700mb on disk but that could be up to 2gb when installed, keep that in mind. I wouldn't bother with an extensive write-to-zero, it should make absolutely no difference.
Have you thought of using virtual machines?
.
