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. To create and format a partition, see Create and format a hard disk partition.


  • Reformatting and repartitioning your hard disk deletes all information on that disk. If you are running a previous version of Windows and want to partition your hard disk without reformatting it, use disk partitioning software, which is available from various manufacturers. Some disk partitioning software allows you to keep your information. If you’re already running the most recent version of Windows and want to partition your hard disk, see Can I repartition my hard disk? Before installing Windows, be sure to disable all antivirus software and back up your files to an external hard disk, a CD or DVD, a USB flash drive, or a network folder.

  1. Turn on the computer running your current edition of Windows, and then insert the installation disc into the computer's CD or DVD drive.

  2. On the Install Windows menu, click Install now.

  3. 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.

  4. 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.

  5. On the Please read the license terms page, if you accept the license terms, click I accept the license terms.

  6. On the Which type of installation do you want? page, click Custom.

  7. 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.

  8. Click Next to begin the installation. You might see a compatibility report.


  • To set up a multiboot configuration on a computer that does not yet have an operating system, partition the hard disk so each operating system you want to install has a partition, and begin by installing the oldest operating system first.

  • Any programs and drivers that you want to use must be installed on each operating system that you want to use them in.