How can I repair a hard drive that Disk Utility and Disk Warrior can't fix?
Many problems can cause such a problem. SMART status is unreliable, but it's good that it's at least 'OK'.

If you don't care about data and just want to format and repartition your HDD then you can:


Check the disk for bad sectors. If it contains bad sectors it may be not a good idea to use such a disk at all. Here are some nice tools that can be used for this.
wipe the disk using dd (make sure that you wiping right drive):

dd if=/dev/zero of=[path to device] bs=1M
Partition it using Disk Utility