The ideal installation should consist of these (to be politically correct, I lifted these from Microsoft) :
- Have at least two partitions. One partition must include the drive Windows is installed on. This is the drive that BitLocker will encrypt. The other partition is the active partition, which must remain unencrypted so that the computer can be started. Once you've encrypted the drive Windows is installed on, you can also encrypt additional data drives on the same computer.
- Be formatted with the NTFS file system.
- Have a BIOS that is compatible with TPM and supports USB devices during computer startup. If this is not the case, you will need to update the BIOS before using BitLocker. For more information on updating your BIOS, see Update the BIOS for BitLocker Drive Encryption.
Now, let's talk about present day. There is hope. Just download something known as Bitlocker Drive Prepartion Tool. It will shift you partition and create the additional partition required for Bitlocker. You can either split or merge to make the space. This tool handles it pretty well. After a reboot, you will be ready to enable it. Make sure you follow the steps to save BOTH the key and the recovery key. Make copies of it in as many places as possible and stored them security. Storing it with your dog, for example, will not be "securely".
So, here is the full details and how you can get the tool. Basically, Windows Update :