I recently installed Windows 7 Enterprise Edition on one of my PC. Eager to get my PC up and running with all software I daily use, I skipped activation. When I tried to activate a few days later, I was greeted by this error message:
In the end it turns out that I ot this message because I hadn't entered my product key yet because I skipped activation during setup. To solve the issue, I:
- went to "Control Panel\System and Security\System"
- clicked "change product key"
- entered a valid product key
Windows automatically activated.