Bartool, welcome to the forum.
Here is a guide that may help you solve your problem.
I have been having problems with my two external hard drives since updating to Win 8.1. I have to unplugg the power and plug it back in to have them recognized every time I boot. I am going to follow the guide to see if it helps me, also.
Please click "KUDOS" if I have helped you and click "Accept as Solution" if your problem is solved.