the user registration solution pack wont work for this, simply too much would need to be modified, you are better pf creating this using DataAssist and Security Assist.
Create the database table to hold the information you want to capture.
then create the form in Dreamweaver for the user to input the information.
Use the DataAssist Insert Record behavior to store the information. In the insert record behavior, there is a section titled Session Variable, this stores the inserted record ID to a session, make note of the session variable name.
Now create the download page, the go to Modify -> Security Assist -> access rile manager.
Create a new access rule as:
Click the lightning bolt next to value and select the session variable created by the insert record behavior.
set the Criteria to <>
leave the compare to value blank.
Now on the download page, go to Insert -> WebAssist -> Security Assist -> Page access, select the rule that you just created to restrict access to the download page to only be allowed if the download form is completed.