You can use BitLocker Drive Encryption to help protect your operating system drive (the drive where Windows is installed), a fixed data drive (such as an internal hard drive) or a removable data drive (such as a USB flash drive). The way you unlock an encrypted drive depends on two things:
What kind of drive it is.
What kind of unlock method you chose when you set up BitLocker on the drive.
If you've turned on BitLocker for your operating system drive, you'll be prompted to enter the BitLocker PIN or password, or insert the USB flash drive that contains your start-up key, when you turn on your PC. You need to do this before you can sign in.
Enter your BitLocker PIN or password, and press Enter.
Or, insert your smart card (also known as a security card), enter your smart card PIN and press Enter.
Open Computer by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering Computer in the search box, tapping or clicking Apps, and then tapping or clicking Computer.
Double-tap or double-click the drive you want to unlock.
Enter your BitLocker password, then tap or click Unlock.
Or, insert your smart card, tap or click More options, tap or click Use smart card, enter your smart card PIN and press Enter.
If you turn on BitLocker for your operating system drive, you can set a BitLocker-protected fixed data drive to automatically unlock when you start Windows.
Open BitLocker Drive Encryption by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the top-right corner of the screen, moving the mouse pointer down, then clicking Search), entering BitLocker in the search box, tapping or clicking Settings, then tapping or clicking BitLocker Drive Encryption. Choose the drive you want to unlock automatically, then tap or click Turn on auto-unlock.
You might be asked for an admin password or to confirm your choice.
Insert the drive into a USB port on your PC.
Tap or click the Unlock drive message.
You can set a BitLocker-protected removable data drive to unlock automatically when you start Windows. Insert the removable drive you want to unlock automatically, tap or click More options, then select the Automatically unlock on this PC checkbox. (You still need to unlock the drive a last time before auto-unlock takes effect.)
BitLocker Drive Encryption is only available in Windows 8 Pro and Windows 8 Enterprise editions.
You can temporarily suspend BitLocker protection (for example, to install new software that BitLocker might otherwise block), or you can turn off BitLocker, which decrypts the drive so that it's no longer protected. For more information, see Help protect your files with BitLocker.