BitLocker is a tool in Windows that can be used to encrypt fixed drives, but also operating systems as well to protect your core data from outside intrusion. Go to Settings > Update & Security > Device encryption.
Method 1 of 3:
Windows 10

Go to Settings > Update & Security > Device encryption.

Choose "Turn on". This will enable BitLocker. It may take a while for the drive to fully encrypt.
Method 2 of 3:
Windows 7 and Later

Press the Windows button on your keyboard and "S" at the same time.

Type in "bitlocker" in the search window that comes up.

Select "Manage BitLocker".

Click on "Turn on BitLocker".
Method 3 of 3:
Enabling BitLocker without Compatible TPM

Log on with administrative privileges.

Press the Windows button on your keyboard and "S" at the same time.

Type and select GPEDIT.MSC

On the left pane, select Computer Configuration > Administrative Templates > Windows Components > Bit Locker Drive Encryption > Operating System Devices.

On the right, double-click 'Require additional authentication' at startup.

Click the "Enabled" radio button. Double check that "Allow Bit Locker without a compatible TPM checkbox" is checked.

Click OK and repeat the process for enabling BitLocker in Windows.

Update 04 March 2020
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