I misspoke when saying that you could use the CMS Builder serial number with the Power CMS 2 files.
You can do a manual install of the Power CMS Builder CMS Files though.
The Power CMS Builder CMS Files are ion the users configuration folder.
for help finding the configuration folder, see the common installation issues PDF:
In the configuration folder go to /Configuration/shared/webassist/PowerCMS/CMS you can copy the files from this directory to your site to manually install the CMS System