The CD key is a mandatory requirement for activating the Sourcenext version during its installation process.
It is a poorly kept secret in the retro-gaming community that the SourceNext releases of Resident Evil 2 (and its sibling, Resident Evil 3 ) do not utilize unique, per-disc serial keys in the way modern software does. Instead, the installer generally accepts a universal key that was widely distributed with the software in that region.
If you own the original Japanese DVD, the key is typically located on an insert inside the yellow DVD case .