Today I had a problem with a Amazon EC2 Windows instance. It said “this copy of windows is not genuine”. I tried to activate it, but it kept giving me errors.

After some searching on the EC2 Forums I found this post which helped me out.

In short:

1. Open "C:\Program Files\Amazon\Ec2ConfigService\Settings\DnsSuffixSettings.xml"
2. Remove the extra </RegionMapping> tag from line 34
3. Open "C:\Program Files\Amazon\Ec2ConfigService\Settings\config.xml"
4. On line 34, change the state of EC2WindowsActivate plugin from Disabled to Enabled
5. Stop and Start the Ec2Config service
6. Wait couple minutes and then run slui.exe to verify Windows is activated (for core installation use "slmgr.vbs /dli")