I am alumni. I cannot use the Microsoft DreamSpark Premium after I graduated.
This happens because after you graduate, the DreamSpark Direct Subscription will terminate. According to Microsoft Software License Terms on https://www.dreamspark.com/Student/Direct-EULA.aspx, 2b "The DreamSpark Direct Subscription is a special offering for students. Once you no longer qualify for the DreamSpark Direct Subscription (due to graduation or otherwise no longer meeting the definition of "you" above), your DreamSpark Direct Subscription will terminate; however, you may continue to use the software you obtained prior to termination of your student status subject to the terms of this agreement."
I have to reinstall the Dreamspark application I downloaded. Where can I find the activation key?
The activation key from DreamSpark used to be mailed with your order receipt but not anymore. Kivuto stores your activation key for a limited number of days after you download the program and archives it. Once archived, you cannot access your activation key anymore unless you purchased an access extension.