yes, this can be done using Security Assist. Security Assist was the tool we used when creating the User registration portion of Power Store.
To start with, you will need to add any necessary fields to the PowerStore 3 users table, then export the user data from the existing users table to the power store 3 users table.
next, to be able to use security assist to make modifications to the power store files, you will need to make sure that the power store files are at the root of your Dreamweaver site. I have attached a screen shoot illustrating this.
We have tutorials for adding encryption to the Security Assist registration process as well as working with user levels. they are available in the Solution Recipes section of the Security Assist support page:
any values such as company name from the users table can be stored in session variables when the user logs in, the method of doing this is described in the User Levels tutorial.