Hello Julie,To see how the registration code attaches to your book think back to when you purchased Activ. You could only view the sample pages until you clicked on the yellow icon of a 'Key,' then entered the registration code. After that the book was unlocked. That's what you'll be doing with your ebook.
Your goal is something I've looked at before. The tricky part is providing a discount if someone has purchased a previous book. Virtual Vault may or may not be able to handle this for you, but I think it may be of value for you to first determine what is important to your marketing.
One of Activ's strengths is that you can let people view a portion of your book, say the first three pages or the first page and two pages from the middle--basically you have complete control of which pages can be viewed before the book is unlocked. Even after a book has been purchased and unlocked and a copy is passed onto a friend, the friend will only see the sample pages until it is puchased.
This type of marketing is called viral marketing because it allows friends to pass the ebook on to friends, while also requiring the purchase to unlock the book. The biggest problem with Virtual Vault is that you must create two separate ebooks: one a sample of the book and the other the purchase version. If Virtual Vault appeals to you please be aware that there is a monthly fee for the service.
An alternative to Virtual Vault that works with Activ's viral marketing approach and at the same time providers the registration code for the ebook at the moment the sale is made is MicroCreations Automatic Payment System.
http://home.att.net/~microcreations/
Both systems require you to use a third party payment system. Microcreations' APS system only works with ClickBank and PayPal so if you have another payment system it may not work for you.
Although Virtual Vault has some good features and may be your ideal solution be aware of the user's experience with such a system. Also, consider the monthly maintainence fee. The geatest strength is that when someone is given a refund the ebook is relocked. The same thing can be achieved with Gold Panner's HYPrLock.
http://www.goldpanner.ca/hyprlock/index.htm
With HYPrLock the user requesting a refund provides a code that shows the ebook has been relocked.
As for the discount you might want to consider having two version of each book (regardless of which of the two systems just mentioned.) After someone makes a purchase you email them a special link to the ebook(s) attached to the discounted price. The link could also have an expiration date so if they don't act if the next 7 days (for example) they will only be able to obtain the book at full price. I'd suggest to seriosly consider a time limit for several reason chief of which the email link could be passed among friends. Unfortunately, the down side is that with viral marketing is if the discounted ebook is shared with a friend the friend will also receive the discount.
As for redistribution with Virtual Vault everything is geared towards preventing an ebook from being shared with a friend. In viral marketing redistribution is encouraged because the more hands the ebook gets into the greater the potential sales. It gets back to how your marketing needs are best served.