I installed Windows 7 from an existing Windows Vista installation (not through a DVD boot).

On the original Windows Vista installation, the partition I'm installing to is listed as D drive. After Windows 7 installation is completed, I realized that the Windows 7 had used D as the drive letter for the system. It runs perfectly fine, just annoying when you have everything on D (instead of the regular C).

Is there any quick painless way of renaming this system drive letter to C? I'm also considering the option of reinstalling from my Vista installation (it is on a different partition, so it is still intact), but would like to know which step it is that will use C as system drive letter?

  • Do you remember how you did succeed installing Windows 7 in a different drive ? What is the value of %SystemRoot% ? D:\Windows ? – NN_ Apr 23 at 17:37

You can't change the letter of a system partition.

If I understand you correctly, you installed to a second partition from inside Vista. This means that your drive is D:\ - it's set as D: because Vista has control over the MBR.

Because both partitions use the same MBR (and boot loader) I believe it's impossible to have two drives referring to the same letter.

  • Right... I guess for now I'll use D as system and E as secondary. – Adrian Godong Aug 7 '09 at 19:40

If you boot to the CD instead of installing from Vista, and you select that same partition to install to then the drive letters will flip flop depending on which OS is running. The C: drive will be the drive that the currently booted OS is installed on.


There is no painless way to move windows from D drive to C drive, actually there is no way to do so as far as I know.


Disclaimer: I have never, ever, tried to do this on the main drive letter, this might break your system entirely—I don't know. Do this at your own risk.

You can go edit the registry key names for your mounted devices:

  1. Go to Start, Run (or type Win+R), and type in regedit.exe
  2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
  3. Find the drive(s) you want to change, look for the \DosDevice\X: keys
  4. Rename them to what you want them to be
  5. Reboot
  • 5
    I wouldn't do this. There are a ton of system variables that are set on install, such as %program files(x86)% %windir% and many others and changing this key will not change those which will caluse pretty much everything to break. – MDMarra Aug 23 '09 at 0:18
  • Good point, Mark. I didn't think of those possible ramifications -- but I knew something along those lines would be a bit off, thus the disclaimer at the top. – Alex Lyman Aug 23 '09 at 8:08

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