I recently installed Vista from scratch. I have three drives in my rig. Two of them were empty at the time of install. The other had all of my junk on it.

Post install, I fired up Disk Management to change drive letters and whatnot, as I wanted the drive with all of my junk on it to be my D drive. I had my C drive with Vista on it, my D drive which was empty, and my E drive which had my junk.

Well, Disk Management had:

  • My C drive marked as: Boot, Page File, Crash Dump, Primary Partition.

  • My D Drive: (empty disk): System, Active, Primary Partition

  • My E Drive: Primary Partition.

Due to my D drive being marked as System, I wasn't able to reassign a different drive letter to it. In fact, Vista wouldn't let me do anything to it, besides disabling it. I did disable it, and was able to then assign D to my drive with all of my junk on it.

Upon re-enabling the drive, it was assigned E, and is still marked as System, Active, Primary Partition. I also did mark my C drive as Active, which didn't accomplish anything.

I want to make this drive, now marked E, my P drive that will host my Page File. However, since it's marked as System, I can't do anything. I can't change drive letters. I can't format it. I can't delete the volume. Every time I try and do one of these things, Vista replies with "Windows cannot (the action) the system partition on this disk."

How can I make my C drive my "System" drive, so I can then manipulate my blank E drive? Also, why is this E drive marked as System anyways, as I installed Vista on my C drive?


The volume marked as "System" was picked by Vista's installer to hold the Windows Boot Manager (and related files) because it's on the disk that your system's firmware (BIOS) thinks of as the default boot device. This can often be tweaked in your system's BIOS menu, but then you will also need to copy all of the necessary files over to the volume on the disk you select as the default boot device instead. (And you'll also need to make sure that the "new" system volume has its partition's "active" bit set, but it sounds like you've already done that.)

Could you clarify what you mean by "disabled" the drive?

(Also note this article that documents the "MountedDevices" registry key and how it controls drive-letter assignments.)

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  • I changed my BIOS's boot drive to my real system drive and reinstalled Vista. Everything is good now. Thanks again! – Aaron Daniels Sep 7 '09 at 18:07


Use Acronis Disk Director Suite..

You can assign the Letters to the drives. The Letters will be changed during the next boot.

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  • Worked for me. I believe it has a trial version available. – alex Sep 7 '09 at 12:19

I found another (free) way of doing this, which doesn't require a Vista DVD:

  • create a bootable recovery disk using Macrium Reflect Free (http://www.macrium.com/reflectfree.aspx), selecting the Windows PE (not Linux) version
  • disconnect the D: drive physically
  • boot using the Macrium Reflect disk
  • repair the file system from there
  • reboot
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