I have a copy of GuitarHero Warriors of Rock (for Wii) and I want to import the songpacks from GH Metallica and GH Greatest Hits in the store. It is a used copy, but the previous owner says that he never used the code to download content. I have enough Wii-points for the purchase. The problem is that I'm asked to enter the 20 digit unique user ID found on the back of the booklet in the case. But I only have 16 characters. I've tried only entering the 16 characters and pressing enter, I've tried to fill it up with zeroes after, and I've double and tripple checked the codes, but nothing works! What should I do?