My apologies in advance for the length of this...

Several days ago, I thought I had lost a Harddrive that was in a 2nd-drive Ultrabay. This got me thinking about drive encryption should this have happened for real. Fortunately I found the drive, and backed-up all the new incremental files.

First - it's a T-61, with Win 10 x-64 that I've put a SSD into, reserving the old HDD for archiving and restoring disk images (made with Acronis True Image 2015). The HDD "lives" in a "generic" Ultrabay caddy. The old drive still has its original partitioning in 3, a Active System C: (Windows 10), and back-up D: and E: partitions. The SSD is partitioned identically.

So I read through some material material on BitLocker, understanding the the Atmel TPM is accessed from the BIOS Security area. I checked the Win 10 Device Manager, and saw no sign of the Atmel TPM chip.

So I set the TPM to "Active", and not knowing if this had ever been used before, I cleared the contents. From there I rebooted, and now saw the Atmel in Device Manager. From there I went to BitLocker and looked at the set-up. What I saw were all 6 disk partitions (3 from the SSD, 3 from the HDD), all with BitLocker off. I'm not sure precisely what I did next - I think it was to set the TPM ready to be used, but I never set any of the partitions to BitLocker On. I may have turned the TPM off in Control Panel, then Rebooted, and set the Atmel TPM to disabled in the BIOS.

What I ended up with was catastrophic mess. The SSD was fine. The HDD wasn't. I found I couldn't open Office files as I lacked permission to do so. My Quicken files couldn't be opened either. However, if I copied the files, they would open, albeit with error messages that Word couldn't find its Temp files.

So, to make things simpler, I took the SSD out and put the HDD back in. (The DVD drive went back in the Ultrabay for a Win 10 install disk or the Acronis recovery disk.)

So I tried...
1. making sure the Environment variable %USERPROFILE% was correct, using a dump of all Environmental Variable using a command line Set command.
2. rebuilt the MBR and the BCD file after getting boots that gave me the choice of "Windows 10" (the "real" active partition), and a "Windows 10 Pro" option that gave a reboot.
3. looking at DISKPART which looked okay (but no partition listed as Active, just Primary)
4. making sure the the C: drive was "Active" (I could be mistaken, but at one point the 500 MB hidden partition may have been Active, and I changed it back to C: drive to be active.

Finally I gave up, and just re-imaged the C: partition.

So all this brought up the following questions:
1. Should one ever try doing BitLocker when two disks with active Windows partitions exist on each?
2. What happens when one take a Bit-Locked drive from one TPM activated T-61 to another one (either TPM-activated or not)? I assume that each TPM T-61 is encoded differently.
3. Why did the SSD survive all this without problems, but the HDD did not?
4. Is this something peculiar to T-61s and the Atmel TPM chip, or does this happen on any older BIOS-type machine vs UEFI?