Encryption with dual block. How to do it right?

Question

Encryption

For example, we have a machine with a dual block.
Two axles spin on it. One - for example Ubuntu, the second - Windows.
The second OS is needed purely for specialized software.
The main system is Linux.
Problem: There is a need to use full disk encryption of the entire HDD.
Question: What is the right and best way to do all this?
In the same Ubuntu there is a regular system. For Win previously used TrueCrypt 7.1a

Answer 1

On some laptops and MPs, there is a trigger in the BIOS that encrypts the hard drive. When enabled, the password for the hard drive will be requested during POST. Further everything is transparent for any OS. Without a password, the hard drive cannot be read even by rearranging it in another computer. Good luck.