Step 1.
If you have not tried it please try to reboot and go to the command prompt again type chkdsk /r again and if it works great if not go to step 2.
Step 2.
Locked volume unlock
diskpart
list volume
select volume xxx (where xxx is the write protected problem drive)
attributes volume clear readonly
exit
chkdsk /r
If it works great let it run if not reboot and try it again.
Step 3.
Please let me know the results.