The machine was installed previously with the Home Premium trial version. The problem is, I had the Professional key to activate but Windows rejected it (because of the version difference). So I thought I had to do a complete reformat and reinstall to upgrade it to Windows 7 Pro.
Thankfully, I did some research (googling) and found the easiest way to upgrade from one Windows version to the other.
The solution is…. Windows Anytime Upgrade. Windows Anytime Upgrade, apparently, is a built-in application on a Windows 7 installation to upgrade from an existing version (say Home Premium) to another (Professional or Ultimate). To access Windows Anytime Upgrade, simply search for it on the Start Menu. Follow the instructions to upgrade (which pretty much just requires clicking buttons and such).
In about 10-15 minutes, my Windows 7 Home Premium trial has been upgraded to a fully working Windows 7 Professional without having to reinstall anything. All Windows settings, wallpapers, files, documents, programs, etc are in tact. Note that this was done on a the MacBook Air (dual-boot with BootCamp).
So before you think of reformatting your Windows 7 machine to upgrade its version/edition, stop!
For further information, check out Windows Anytime Upgrade over at Microsoft.
Thank you, Microsoft. It can’t get any better than this.
