Lets say I need to map folder C:/D as drive D:

One can use SUBST command to map folder as drive in Windows.


I am absolutely happy how SUBST does the work. So I set this command as a startup task using the task manager.

A problem here is that if I have a flash in a USB port while booting Windows, the flash is got mapped as D: and SUBST fails.

The question is how to make C:/D to be D: permanently. So other drives (especially flash drives) don't break this during startup.

P.S. I know I could set D: to be R: which is unlikely to conflict with other drives. But I would greatly appreciate another answer.


I found some posts here, apparently you can make it persistent with a registry modification: How to make SUBST mapping persistent across reboots?

Granted I haven't tried this myself...

  • 1
    Thank you very much. Indeed using the "...\Session Manager\DOS Devices" registry entry solved the problem with early drive initialization.
    – MajesticRa
    Apr 6 '12 at 9:40

you can use this utility to solve the conflict. it is called USB Drive Letter Manager for Windows.


  • Thank you very much. The tool allows to set new usb letters. This could help for usb. But there could be not-USB-disks inserted too. I really would love a solution how to 'reserve' disk letter to use it. Some system policy maybe...
    – MajesticRa
    Apr 5 '12 at 21:59

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