access denied to external hard drive

I am trying to access my external hard drive, but keep getting "F:/ not
accessible, access is denied". I can change the name of the "F-drive",
but not access. This is happening even thu I am in Administration
I have recently accessed the same external hard drive to change
security settings to all the files so that all users have full control.
Was this a mistake to do?
there are very important data there that I need to access for my I look at datarecovery software? or is that not gonna get
me anywhere?
Please help.