The article is here: http://www.thewindowsclub.com/install-windows-8-1-separate-partition

It might be a really good idea to do it this way, since you might not want to lose your working OS, especially if it’s Windows 8 with all Stardock’s goodies which turn W8 into something workable.

Stepwise?

1. Create a partition with your software or Disk Management Tool (you can read how to do that here: http://www.thewindowsclub.com/create-new-resize-extend-partition-disk-management-tool )

2. Download and burn the ISO to a DVD disk. The product key is:

NTTX3-RV7VB-T7X7F-WQYYY-9Y92

3. Select the time format, language, etc.

4. Click the “Install Now” button.

6. Accept the Licensing Terms and click “Next”.

7. Now, since you’re installing W8.1 on a separate partition, click “Custom Install” and you’ll be asked where. Choose that location from the list presented to you.

8. Your computer will reboot twice during the installation.

9. Then you’ll be presented with the choice of OSs to boot.

Thanks, AnadK@TWC!