When I open Bitlocker in Control Panel I see a message, Your system is not configured to use Bitlocker Drive Encryption. If there is a bootable CD or DVD in your computer, remove it, restart the computer and turn on Bitlocker again. If the problem persists contact the computer manufacturer for BIOS upgrade instructions. Background: 4.5 years ago I bought a Lenovo Thinkpad R61 laptop with Vista Ultimate specifically to get Bitlocker. Used Drive Preparation Tool and all was fine for a couple years. Successfully changed to bigger hard drive. I don't remember the details. A couple more years, then two or three months ago I bought a 1TB HDD and had a terrible time getting the clone utility from HDD mfr to work. Finally turned off Bitlocker, completely decrypted the drive (nowhere in any instructions), turned off TPM and clone worked. Installed. Used unencrypted for a couple months. Now I want Bitlocker on again and it will not turn on. I've been working on it for two days. When I run the Drive Preparation Tool it says my computer is already configured for Bitlocker, yet Control Panel reports that it is not in the bold message above. Disk Management reports all three partitions (third is mfr. recovery) are Healthy. TPM shows it is back on and I have taken ownership of it. Today I cleared the TPM which later reading indicates may have been a mistake. S drive will not let me format it so DPT can recopy the files it needs if one is corrupt. I have never changed the boot order of the computer; DVD, USB, HDD 0. I can do a restore to factory delivered condition and rebuild everything from backup, but I thought someone might know an easier fix. Thanks for your time.