Reasons Microsoft does not support booting Windows from external drives

Some of us love to install and carry Windows on USB Drives. But these are scenarios that Microsoft does not support. It is unsupported to boot Windows from external devices. Such installations are not supported.

If you do decide to install Windows to USB drive, a Flash Drive(UFD) drive, ESATA drive or store Windows 7 Native Boot VHD on USB/UFD drive, it will not be supported by Microsoft.

The reasons why this is not supported have been mentioned in KB2485453:

  1. Activation issues.
  2. Potential Boot Path support issues.
  3. You must disable the device write cache or click ‘safe removal’ before unplugging the cable. Otherwise, there could be a data loss.

However there are some specialized products which support this type of scenario, viz. installation on external drives :

  • Windows 7 Embedded supports this scenario
  • Microsoft Hyper-V Server 2008 R2 supports the ability to boot from a USB flash device (UFD). Booting Hyper-V Server 2008 R2 from USB flash drive is only supported for OEM’s.

Just so you know! 🙂

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Anand Khanse is the Admin of, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP. Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.