Windows 8.1 released today. I’ve been using it since they released it to Technet and MSDN subscribers last month. It’s had an annoying “Test Mode Windows 8.1 Pro Build 9600” message on the desktop since I installed it. I finally took time today to find out how to get rid of it.
Launch a command prompt as Administrator.
Type: bcdedit -set TESTSIGNING OFF
No more Test Mode message.
Update (10/20/2013): I’ve had one commenter say this doesn’t work for non-Pro versions of Windows 8.1. I haven’t verified this.