If you have a valid serial but it won't "stick," you may need to delete the HKEY_LOCAL_MACHINE\SOFTWARE\Sony Creative Software
The term "90c" refers to a specific (version 9.0c) for Sound Forge Pro 9.0. This update was released by Sony Creative Software (Sony sold the software line to MAGIX in 2016) to fix bugs and improve stability in the version 9 series. sony sound forge 90c authentication code upd