
Explanation/Reference:
Install more than one operating system (multiboot)
When you install the new version of Windows, you can keep an older version of Windows on your computer.
This is often called a multiboot or dual-boot configuration.
Before you begin: Make sure that your hard disk has a separate partition for each operating system that you want to install, or that your computer has multiple hard disks. Otherwise, you will either have to reformat and repartition your hard disk or install the new operating system on a separate hard disk. Also, make sure that the partition or disk where you plan to install the new version of Windows is formatted with the NTFS file system.
Turn on the computer running your current edition of Windows, and then insert the installation disc into the computer's CD or DVD drive.
On the Install Windows menu, click Install now.
On the Get important updates for installation page, we recommend getting the latest updates to help ensure a successful installation and to help protect your computer against security threats. You must be connected to the Internet to receive installation updates. This page might not appear if your computer is not connected to the Internet.
On the Type your product key for activation page, we strongly recommend that you type your 25-character product key to help avoid problems during activation.
On the Please read the license terms page, if you accept the license terms, click I accept the license terms.
On the Which type of installation do you want page, click Custom.
On the Where do you want to install Windows page, select the partition or disk where you want to install the new Windows operating system.