Ubuntu :: Can't Unmount External Hard Drive

I have an external hard drive which connects to a usb port. until recently i could unmount it by right clicking on the desktop icon and selecting unmount. now when i try that it tells me that i can't because the device is not in fstab and i am not the root. i checked mtab and it had this line '/dev/sdb1 /media/usb0 msdos rw,noexec,nodev,nosuid 0 0' i changed that to '/dev/sdb1 /media/usb0 msdos user,rw,noexec,nodev,nosuid 0 0' thinking that would fix it, but it didn't. i unmounted using 'sudo umount /media/usb0' and restarted my computer and now the line in mtab reads '/dev/sdb1 /media/usb0 vfat rw,noexec,nodev,sync,noatime,nodiratime 0 0' and i still can't unmount without using the sudo umount command. i also tried adding '/dev/sdb1 /media/usb0 msdos user,rw,noexec,nodev,nosuid 0 0' to fstab and that didn't help