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Possible Duplicate:
Phantom hard drive after deploying latest Windows 7 image from WDS

This is a really weird issue which is the reason for the vague title; sorry.

The following screenshot shows a few local disks on my machine. The only problem is I only have one disk and it is correctly represented by C:. local disks

Disk Management shows no problems. The "fake" local drives are pointing at My Documents. They're labeled W: and X:. There's also a Y: that shows up in the sidebar with a question mark (left sidebar in the screenshot above Freehold).

What is going on here and how do I fix it? I've never seen anything like this.

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marked as duplicate by Synetech, Simon Sheehan, random Mar 14 '12 at 16:38

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Are you a member of a windows SBS domain? – G Koe Mar 12 '12 at 21:25
up vote 6 down vote accepted

The W: and X: drive letters might be mapped using DefineDosDevice(), which can be controlled using subst from command line. (subst has been a common way to map a directory to a drive letter since MS-DOS times.)

Run subst to list the mappings; use subst /d w: to delete them.

Y: might be caused by a similar mapping to a non-existent location, in which case subst /d y: would remove it as described above.

But there can be other causes for it; for example, on my own system I've had a new iTunes component (APSDaemon) freeze leaving such an "unknown" drive in place of sister's iPod. There could also be other, even more unlikely reasons.

If you want to dig deep, WinObj would show what each drive letter points to. In the tree displayed, global devices are under \GLOBAL??, while local devices for each logon session are under \Sessions\sid\DosDevices\luid. You might be able to track them back to weird device drivers or such.

WinObj WinObj

(Please excuse the lack of freehand circles.)

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+1. The fact that the drive sizes are identical suggests they are all the same drive. SUBST it is. – shufler Mar 12 '12 at 22:14
That was it. Thanks. Now that I understand what it is I can guess at the cause. I think an app called PureSync caused the issue when I tried to sync a mapped network drive folder to a local drive folder. – GollyJer Mar 13 '12 at 17:01

Whenever you see a bunch of identical disk (that are not part of a RAID), the most likely cause is subst.

  1. Open a command-prompt (cmd.exe)
  2. Type subst to see a list of mappings
  3. Type subst w: /d and subst x: /d to delete them

Of course if you did not do it yourself (as your question seems to imply), then the question becomes how, where, and when did they get mapped.

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