Setup Requires Format of Initial Partition If You Install to a Subsequent Partition on a Hard Disk

This article describes the behavior of an installation to a partition which is unformatted and is not the first partition on the hard disk.

When you install Windows XP on a computer with an unformatted hard disk, if the hard disk is partitioned into more than one hard-linked partition (either by using FDISK or text-mode Setup), you can choose to install to a partition other than the first partition. However, before Setup starts, the initial (system) partition(s) are automatically formatted with the file system that was chosen for the boot partition. By design, the formatting of a subsequent partition before the formatting of the initial partition is not allowed. This is because Setup must format the first (system) partition of the primary drive to store the required Windows XP start up files, such as Boot.ini and Ntldr.