Hi,
- Have you already locked the drive using bit locker or are you trying the lock the drive?
Here are a few steps you may try and let us know the outcome.
- Please unplug all the external hardware devices attached to the computer. (mainly the scanners and the printers).
- Change the power setting to never turn off the Computer.
- Type Power Options in the Search of the Charms bar.
- Click on "Change when the computer sleeps"
- Change the setting to Never for "turn off the display" and "Put the computer to sleep"
Let us know how it goes after you try these steps.