A lot of users are seeing this new drive, it is the recovery drive, it is not meant to have a drive letter, remove the drive letter and everything will return to normal:

Click your Start Button, type cmd, then right click Command Prompt and choose 'Run as Administrator'

Run this command and hit Enter

diskpart

Run this command and hit Enter

list volume

Note down the letter associated with that new drive

Run these commands one at a time and hit Enter (replace X with the correct drive letter)

select volume X

remove letter=X

Close Command Prompt and restart your PC