I've searched around the forums here, and it seems some similar questions have been asked like this in the past, but now the threads are over a month old, and I don't want to bump them. Plus, maybe this can serve as an FAQ, and let other people know what contributions or methods would be best for achieving this goal.

Here's the plan:
* We have Product X
* Product X normally sells for (let's say) $100.00
* We offer Product X at our regular price, and as a free evaluation/demo/trial/whatever ($0.00 cost)
* Customers can only get Product X for free ONCE
* Product X can be bought by Guests and Customers (people that make an account)
* Coupon codes are not a good way of doing this, as once the code is out, everyone can get it for free.
* Email address verification (for Guests that have no account) could be used, but then people could just use different email addresses, also leading to infinite free trials
* Tracking IPs could also work, but if a person changes their IP....
* Names and addresses could also be faked
* The only way to resolve this is to trust that people won't abuse the system

Questions:
* How would we implement a one-time free purchase of Product X?
* Would the easiest way to be to make a new product that simply has a cost of $0.00?
* How can we skip payment if the Grand Total is $0.00?
* Should we force Guests that get the free trial to create an account to prevent further abuse?

I'll need to talk to the person who's running the show over here to see what he thinks of all of this, and if he cares about the minute stuff like I do.

Thanks in advance for any and all suggestions.