Drive as in root of the drive, not just a subfolder.
The only way this problem can occur is if the previously set permissions of the drive has the check mark to inherit child permissions, in which case any previously set permissions of the drive are being inherited by the folder you are having problems changing the permissions on.
Also, if you don't show up as the owner of this folder or drive it may help to take ownership.
Another problem appears to be that for some reason you aren't using the NTFS permissions on this folder and you seem to be stuck using the Homegroup permissions, I'm not sure why this is happening unless this drive or folder was somehow added to the Homegroup folders.
The details of this get fairly complicated although Brink's tutorial explains the process pretty well. Permissions - Allow or Deny Users and Groups