Thoughts from you about a bad drive

Hi. I know nothing about this stuff so excuse my terms of describing this problem. I have an external USB HD that has 4 WD HD’s in it. You can slip them all out individually and replace them. It’s about 2 years old. One went bad and WD replaced it already.  I’ve been trying to use the WD Backup Software and it kept having errors. I tied to manually copy some of the folders and it said that it couldn’t read them (movies) even though they played fine. Does this sound like the drive is going bad? I’m trying to back up as much as will copy right now so I can’t pull it out. There about 126 movies on it so it’s taking forever.

Hi the only way to know is to test the drive you can use a trial copy of hd tune or run the WD diagnostic tools. they are called Data Lifeguard Diagnostic and you can get them from WD site