Nero 6 was released in mid-2003. The initial release was version 6.0.0.9, which was notoriously buggy. Over the following months, Ahead Software (the original developer, later Nero AG) pushed several updates. Build 6.0.0.23 arrived in late 2003 and was considered one of the first releases of Nero 6.
Searching for a "Nero 6 serial number" today is risky.
For modern and legacy Nero software, serial numbers are managed through the or Nero Start .