|  | Upgrading to Windows XP Professional Installing Windows XP Professional in a Dual-Boot Configuration
A dual-boot configuration enables you to choose between two or more operating systems each time you start the computer. By using this type of configuration, you can run applications that are not compliant with Windows XP Professional on an existing operating system, while using Windows XP Professional for all other applications.
| Important: Some operating systems, such as MS-DOS, do not recognize partitions formatted with FAT32 or NTFS file systems.
The active partition is the partition from which the computer starts, and it must be formatted with a file system that is recognized by both operating systems. For example, the active partition must be formatted with FAT when you have a dual-boot configuration with MS-DOS and Windows XP Professional, or FAT32 when you have a dual-boot configuration with Windows 98 and Windows XP Professional. The other operating system must be installed first, and then you can install Windows XP Professional on the active partition or on another primary or extended partition. When you choose to install Windows XP Professional on a partition other than the active partition, Windows XP Professional will copy the necessary files to start the boot process to the active partition, which is referred to as the Windows XP Professional system partition. This enables Windows XP Professional to begin the boot process. The remainder of the operating system files will be copied to the non-active partition, which is referred to as the Windows XP Professional boot partition.