I have a hard drive with a Win 10 installation and BitLocker enabled. I can shrink that partition and install Windows 10 in the unallocated space, but when I enable BitLocker on that partition, it becomes unmountable, Windows will not boot anymore with an error saying it's unmountable. I tried a few different ways of doing it, making them both unencrypted and then encrypting the first one and then the first one becomes unbootable. I noticed when I enabled BitLocker, Windows shrunk the partition and added a recovery partition at the end, so I ended up with 2 recovery partitions.
I believe I'm done attempting that scheme and I'm just going to buy another hard drive. Would that work, 2 hard drives, 2 Windows 10 install, both with BitLocker enabled and a selector on boot that allows me to choose which one to use?
Would I be able to put one partition to sleep while I use the other?
21 Answer
The problem you are running in to is likely due to how Windows stores the key to unlock the partition in your platform TPM. When you activate Bitlocker using a TPM, Windows clears the TPM and installs a fresh key for use with the encryption. This is why you lose access to your first install.
You can have multiple TPM devices (one provided by the CPU and one provided by a discreet TPM chip) but only one may be active in UEFI at a time. Changing the active TPM would invalidate secure boot. So even that is not a solution.
The only way to have what you want is to make one of the Bitlocker deployments ignore the TPM. You can control this using group policy. It will be less secure because you will have to store the key in plain text on a USB drive. For this reason you should use a different PIN for each of the two partitions.
The settings that are available can be seen here:
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