I set up a friend with 12.04 and he forgot his password. I encrypted his home directory and I have written down the encryption passphrase during the first boot. If he changed his password after I wrote down the encryption passphrase during the first boot is this original encryption passphrase of any use? What should I do to reset or recover his password and keep everything accessible and functionally intact with the encrypted home directory?
The passphrase for encrypting the drive is not affected by the user password, it is merely encrypted by the user password. If you change his password, the new encryption should be applied to the passphrase, meaning that the passphrase will still be the same, but the encrypted version of the passphrase will be different. The drive is not re-encrypted by changing your password, only when you change your passphrase.
For assistance with changing his password, look here