Take Control of VMware Fusion 2 Series: Windows Activation

Unlike Mac OS X, Windows requires a serial number (called a product key) as well as an online activation process that ties your product key to one particular hardware configuration. When you purchase and install a retail copy of Windows for the first time, activation is simple. The Windows installer normally prompts you to activate at the end of installation; if it doesn’t (or if you ignore the prompt), you’ll see a pop-up notice in the system tray (in the lower-right corner of the screen) saying that you must activate the product within 30 days. Click this notice, and then follow the instructions to activate Windows. (After 30 days, you won’t be able to start Windows without activating.)

Behind the scenes, Windows records several pieces of data about your hardware, as well as your product key, and sends that data to Microsoft.

If you later try to activate a copy of Windows with the same product key but on substantially different hardware, Windows prompts you to reactivate. It overlooks certain minor hardware changes, and in some cases you can easily reactivate after adding, removing, or upgrading hardware. But if Windows suspects that you’re trying to violate your license agreement by reusing the same product key in two completely different places, you’ll be forced to call Microsoft. If you can convince the person you’re speaking to that you haven’t circumvented your license, you’ll be given a long code that you can enter to reactivate Windows.

A copy of Windows running under Boot Camp sees your Mac’s actual hardware, but Windows running Fusion sees the virtual hardware that Fusion creates to simulate a PC. So, if you activate Windows under Boot Camp and then try to use the same copy (with the same product key) in Fusion, you’re prompted to reactivate. See the section “Use a Boot Camp Partition in Fusion” for details.