Disk Utility Stuck while Erasing

I am using Macbook pro mid 2012. I was having several problem with my Macbook. Few days back, my mac went to sleep mode but after that when i tried to turn it on, it didn't. I pressed the power button for a while to shut down. After that when i tried to re-open it, it didn't. Then i re-isntalled the OS X in an External HDD and it started working.

Now i was trying to format the internal HDD to do a clean install of OS. I have two partitions. When i try to erase one of my partition, it gets stuck in the middle for several hours. Any solution?