If it's not sensitive data, as you stated, I would just format the drive a couple times, full format not quick, and reinstall windows.
If you really want it gone forever, you have to format it, write data to the entire disk (usually zeros 0000000000), and then format it again, more zeros, and format, and more zeros. You get the idea.
But again, this takes time.
To me, it is kind of like shedding mail, then burning it, then burying it, then mulching it, then planting flowers over it.
If I am going to take the time to do it, it had better be something that I REALLY want to get rid of.