It may take a few steps, but here's how to do it:
1. Go to
www.blockbuster.com/laptop
2. At the very bottom, click the two small dots in the lefthand corner
3. Enter: 06981
bbonline
Now you can fill out the form and at the confirmation page print out your free movie rental coupon.
This can be done even if you've already had Blockbuster Online!