If you lost the registration key for the SlingPlayer Mobile application, check the order information that was sent in the confirmation e-mail, or go to the Sling Media Store and click order status. When the order information screen appears, log in with the second option using your e-mail address and the last five digits of your credit card that you used for the purchase. The results page opens and lists the processed orders. Click on the order number for the purchase. On the details page, scroll down to the product name. The registration key is listed there.