We all know that Windows supports only four primary partitions per disk drive, but what you may not know is that this can affect installing Windows operating systems. For example, when you try and install Windows Server 2003 on a machine that already has four primary partitions containing data on its drive, Setup will fail with the message “Setup cannot create a new partition.” What’s weird though is that I heard that someone got this message when there were only three primary partitions on the system, so Setup should have been able to create a fourth partition, right? What went wrong?

A quick examination of the system revealed that there was a hidden disk utility partition on the drive that had been put there by the OEM from whom the system had been purchased. Moral of the story? Those OEM partitions count as primary partitions and can therefore limit your flexibility in installing Windows on machines where data partitions already exist.

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Mitch Tulloch was lead author for the Windows Vista Resource Kit from Microsoft Press, which is THE book for IT pros who want to deploy, maintain and support Windows Vista in mid- and large-sized network environments. For more information see www.mtit.com.