How do I run a operational check on my hardware?

I would like to check all my hardware for problems and to make sure they are all running properly. I am not sure just how to do that. Can anybody help?

I would also like to know is there is a way to check my external hard drives for proper operation. I had removed two suspected corrupted internal hard drives. I there a way to check them no that they are removed, to see if they are recoverable?