On old versions of Windows, replacing a Windows product key required using a special tool, and upgrading from one edition of the system to another required a new installation. On Windows 7, these tasks only take a few steps and won't erase any of your files. If you're switching product keys for the currently installed version of Windows 7 -- such as if you entered the wrong key during setup -- use the "Change Product Key" link in the System Control Panel. To move to a different edition, such as from Windows 7 Home Premium to Windows 7 Ultimate, use the Windows Anytime Upgrade utility.
Open the Start menu, right-click "Computer" and choose "Properties" to open the System Control Panel. Alternatively, right-click the "Computer" icon on your desktop, if you have one, and select "Properties."
Click "Change Product Key" at the bottom of the window. You might need to scroll down to find the link. If Windows prompts you with a User Account Control warning, press "Continue."
Type in the new key, found in the packaging of the Windows installation disc or on your receipt if you purchased a license digitally. Press "Next."
Wait while Windows activates the new key. If activation fails, make sure your computer is connected to the Internet, retype the key and try again.
Search for and open "Windows Anytime Upgrade" in the Start menu.
Click "Enter an Upgrade Key." Alternatively, if you don't own a key yet, choose "Go online..." to buy a new key.
Enter your Windows Anytime Upgrade key and press "Next" to upgrade your computer.
Tips & Warnings
- You can use the **Change Product Key** option to to change your key or upgrade to another Windows edition in Windows 8.1, if you've already purchased a key.
- The steps to change between keys on the same edition of Windows 7 also work to change between two Windows Vista product keys, but not to upgrade from Vista to Windows 7.