Rename or remove the license.dat file in earlier install subdirectories and restart CW to load the proper license.
(I renamed all the license.dat files on the computer and started CW. I got an error that listed the environment variable CW uses to look for license.dat. The LicensePath includes all previous installs, listed in order. When CW starts, it looks through the installs in order so CW v6.3 was loading with a license from v5.0 which is why I couldn't build code bigger than 16k)