Back up hard drive

What is the easiest and/or best way to install a backup hard drive to your pc? I have heard of dual hard drives and external drives but not sure what to do. Had a episode of not having any computer activity going, blank screen. I guess it was the virus protection auto updating but it just crapped out my pc for a few hours.

Also do not know how to transfer data from working drive to backup. thanks

First off what kind of PC, store bought or custom? If store bought could you supply the model number so I can look it up. When you say duel drives are you referring to 2 individual drives as in D: and E: for example, or RAID? Also could you explain the episode you had a bit more?

Externals are pretty much plug and play.

Just uh .. plug it in, there are 2 wires, a power and a data ....

Open windows explorer, copy ... paste.

Just a generic pc from a few years back. That blank screen happened during the time I have the pc scheduled to do updates. I have to assume that the updating was doing the problem. The pc was not running when I went into use it so that puzzled me. I thought the updates have to have a running pc, this one was in rest mode.

I think the external drive will do. Had read one of the external type,(Cruise?) had software to copy the operating system from the other drive.