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I am trying to setup a PC with the following setup:

  1. Dual boot, Win 7 and Win 8.1, each with their own partition.
  2. Both partitions encrypted with BitLocker
  3. At boot time, I select the OS I want to launch
  4. After booting, only the partition for the OS I booted is accessible.

The goal is to make the data in the Win 8 partition inaccessible to the Win 7 partition, and vice versa. So, each system is totally isolated from the other (aside from the possibility of deleting or wiping the partition).

Is a setup like this possible? From what I've read about BitLocker so far, it seems like it encrypts the drive, and then you enter a password at boot time to decrypt it. But I don't want to decrypt everything. I want two separate passwords, one that decrypts only the Win 7 partition, and one that decrypts only the Win 8 partition. Looking for guidance on how I would set this up.

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up vote 1 down vote accepted

Yes, it can be done; I just did it this evening. I installed a new hard disk so it seemed an ideal opportunity to experiment.

My computer does not have a TPM module, so Windows 7's Bitlocker requires a USB stick; this is not suitable but fortunately Windows 8's Bitlocker comes to the rescue.

Here's how I did it on my system; I don't know if this would work for all scenarios.

  • Install Windows 7 in one partition. Don't encrypt it yet.
  • Install Windows 8.1 in another partition.
  • Boot to Windows 8.1.
  • Encrypt the Windows 7 partition with one password.
  • Encrypt the Windows 8.1 partition with a different password.
  • Reboot.

After rebooting, the Windows 8.1 boot loader will prompt for the Windows 8.1 Bitlocker password; at this point you can press F11 to select a different operating system and choose to boot Windows 7, being prompted for Windows 7's Bitlocker password along the way.

Windows 7 will see the Windows 8.1 partition and vice-versa, but the respective partitions will show as locked unless the appropriate password is entered.

This will not stop a user of either operating system from erasing the other partition from Disk Management; it only stops casual snooping.

You can experiment to prove to your own satisfaction that the Windows 7 Bitlocker password will not unlock the Windows 8 partition when booting, and vice-versa.

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Something else I did for my own convenience - it's my computer and no-one else uses it - but which may also assist to discourage snooping on a shared computer (just remember that security by obscurity is no security at all) is to remove the drive letter from the other operating system partition. This means that that Windows 8 won't show the Windows 7 partition in Explorer, and vice-versa. The partitions are still visible in Disk Management, but not shown for everyday use. If I need to have some files available to both operating systems I put them in a third partition visible to both. – user434459 Apr 4 '15 at 7:49

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