I did not get a software key when I downloaded autocollage. My collages are all showing Trial.
When you purchase AutoCollage, a product key is created and deposited in your digital locker (Windows Marketplace) or your Account information (Online Microsoft Store), depending upon whether you purchased in the US or the EU respectively.
For US purchase, you can look up your product key by going to http://windowsmarketplace.com and clicking on 'Your Digital Locker' at the top of the page. Sign in if prompted, and then you will see a 'your software' page which should let you view your License (product key) for autoCollage.
For EU purchase, visit the online Microsoft Store and click on the 'Account' link at the top of the page. This should show your AutoCollage product key.
Once you have your product key, you can register by following the instructions at http://research.microsoft.com/autocollage/Help/BuyingAutoCollage.htm, cut-and pasted below.
We hope this fixes your problem, please let us know if it does not.
Thanks for your question!
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To register your copy of AutoCollage:
Once your copy of AutoCollage is registered, the trial time limit and watermark are disabled.