DVD corruption is common problem that may happen when installing SQL Server 2012, one way to solve this problem is to download SQL server 2012 Enterprise evaluation
Then in product key dialog enter PID for developer edition
Tried doing something similar: had been running the Eval version. Purchased the Developer edition and tried 'upgrading' the Eval version to Developer: wouldn't accept the product key. I was then left with installing a Developer Edition instance and importing the data - which did accept the key. However all of the management utilities have now expired and there is no way to uninstall!
Am now downloading the Evaluation edition again in order to completely uninstall and start again - unless someone can tell me how to get it to accept the product key.