Hello, im not a first time user for Ubuntu but nether am i an expert. my WD 2TB external hard drive is being detected but will not mount so i cannot view or use anything store on my hard drive... when i got in to my storage devices window and try to manually mount i get this as an error in these details.

Error mounting: mount exited with exit code 1: helper failed with:
mount: according to mtab, /dev/sdb1 is already mounted on /
mount failed

if someone can give me some help id be greatly appreciative. i really hope this is a none format kinda fix...... ><"