Contact Form Plugins – Looking for a Specific Functionality

Hi, I have a client who is looking to have a downloading process on their website that involves the following process:

1. A viewer clicks on a download
2. A pop-up form appears for them to enter their contact information
3. The contact form then generates an email to send to the viewer with the download attachment.

The client has over 35 downloads throughout the site, but doesn’t want to make the viewers enter their contact information every time they want to download something, so he wants the form to remember their information and pre-populate it every time they fill out the form after the first entry.

I have the 1-3 process functioning using a pop-up display plugin and CForm Builder, but I don’t know how to get the form to pre-populate with the viewer’s content, other than advising the viewer to allow their browser to use caching.

Does anyone know of any plugins that have this capability or any other ideas on how to achieve this? Perhaps I need to go down the route of membership plugins? Any suggestions are greatly appreciated!

Best,
Karen