The .SQL Scripts that come with UserRegistration Solution Pack and Power CMS contain only create Table Statements. They do not create the database.
When you run the SQL Scripts, you must first Select the database they will be run against.
You can select the same DB for both to have the tables for both merged into the same database.
Just a Note:
The Admin username and password for PowerCMS is set tin the PowerCMS Globals file, it is not configured to use a DB for admin access.