Fixing

First, let's locate the file. Locate it on your Steam folder: >steamapps>>common>>dota 2 beta>>game>>dota>>panorama>>videos>>promo>. There, you will see it: .To fix the lag:1.Delete the fileIt will make your background a simple black solid color. It will your main menu lag, and that is what matters overall.2.Compress the fileIf you still want the animated background, try compressing the file to a lower quality one. So you can fix your lag and still have the cool background. Compress to a point where it does not interfere your performance.