Before updating to v2.x: Please read this general guide: http://transvelo.com/how-to-safely-update-from-mediacenter-v1-x-to-v2-x/
Important Announcement : Before updating to 2.0.0, please make sure you backup your files. Please read this guide : http://transvelo.com/mediacenter-v2-0-0/
Updating via Envato Toolkit from 1.x to 2.x, the theme name has been changed from Media Center to MediaCenter Nulled in keeping with WP standards. This means that Envato Toolkit fails to recognize the theme as being installed. You will most likely get a folder already exists error. To avoid this, please backup all your theme files manually. Once you have backedup, remove the mediacenter folder completely and upload the new unzipped mediacenter folder. This will make sure that folders are replaced instead of being merged. If you are updating from 2.x to 2.x, you can use Envato Toolkit.