HELP! I have a complicated problem copying files

HELP!  I have a complicated problem… cannot back up but a few of my picture files on the WD from Windows 7 at a time.  It only backs up a few and then it stops.  I had to unplug my WD, shut down my computer and restart it again.  It won’t let  me finish a complete back up.

The files are jpgs

Hi dude, how are you making the backup in the first place? o.o