Install more than one operating system (multiboot)

When you install a new version of Windows, you can keep an older version of Windows on your computer. This is called a multiboot or dual-boot configuration. Whenever you start your computer, you can choose which version of Windows to run. For more information, see Can I have more than one operating system on my computer (multiboot)?

A multiboot disk configuration

Multibooting requires separate partitions on your computer's hard disk for each operating system. If you're running Windows Vista, you can shrink an existing partition to create additional unallocated space from which to create a new partition. For more information, see Can I repartition my hard disk?

If you're running a version of Windows earlier than Windows Vista and need to create another partition, use a third-party partitioning program. Several third-party manufacturers offer programs that allow you to repartition your hard disk without erasing data.

Warnings

• You must install the oldest operating system first, and then install the more recent operating system. If you don't (for example, you install Windows Vista on a computer already running Windows 7), you can render your system inoperable. This can happen because earlier versions of Windows don't recognize the startup files used in more recent versions of Windows and can overwrite them.

• Make sure that the partition or disk where you plan to install the new version of Windows is formatted with the NTFS file system. If you are formatting an existing partition that has data on it, all of the data will be deleted. To create and format a partition, see Create and format a hard disk partition.