How to turn off Windows Azure's "This copy of Windows is not genuine" message?

I'm pretty sure this only shows up with OS family 1 (Windows Server 2008 SP2). If you were to change osFamily="2"(Windows Server 2008 R2) in your ServiceConfiguration.cscfg and update your deployment, you shouldn't see that on the desktop. This is where the setting lives:

<ServiceConfiguration serviceName="GenuineTest" xmlns="http://schemas.microsoft.com/ServiceHosting/2008/10/ServiceConfiguration" osFamily="2" osVersion="*">

I just double-checked this with a few of my deployments running osFamily="2". I also RDP'd into one of mine running osFamily="1" and the "This copy of Windows is not genuine" message is there.

Depending on your configuration management practices, it might not be practical to simply change an OS version and redeploy. For demo purposes, it might be worth pushing up a simple single-instance VM (worker or web role - doesn't really matter) running osFamily="2" and RDP-ing into it to show that the desktop has no warning on it.

For more info on OS families, see this page.