It is no longer accessible but the setting still exists in the VS settings file. Close VS2012 first. Locate your settings file, mine is stored in C:\Users\myname\Documents\Visual Studio 2012\Settings\CurrentSettings.vssettings
Open the file with a text editor and search for "anim". There's an "AnimationSpeed" setting, mine is 5. And an "Animations" setting, mine is true. Try changing it to false, save and start VS again. Or tinker with the speed, my setting of "5" doesn't do anything that does my head in. So I don't really know how to test if changing these settings has any effect, but you'll quickly find out.
If you see no effect at all then tinker with the Windows animation settings.