Several posts in this forum tell about a problem when burning lead-out on CD-Rs, using Nero.
According to those posts it happens that Nero keeps running at 100%, never coming to a halt. Several users explain that after that happening their drives don't accept any CD-Rs anymore.
A few days back it happened to me as well, when burning a SVCD (using Nero 22.214.171.124), drives kepts on spinning full speed at 100% never coming to a halt.
BUT: My drive did not break, it's still accepting CD-Rs happily (at least reading, didn't try writing yet).
So here is what I did when Nero didn't stop:
press Abort and WAIT until it really aborts! this may take quite some time.
confirm the abort dialog and wait for Nero to return to the main screen. this will take quite some time again.
quite Nero and shutdown the pc! you cannot make the drive stop and you cannot make Nero open the drive, it will keep spinning until you shutdown.
restart and use the drive happily ever after!