Forgot to mention - when I right click My Computer and go into disk management, C, D, E and M (external hard drive) are reported as healthy.
A S.M.A.R.T message is directly from the HDD internal controller. If it says your drive is failing, I hope you have a back-up
Not enought info here to tell which drive is reporting the issue. A lot of drive vendors post tools to read the SMART data from their drives.
Sounds like you have several choices (C,D,E, OR M)