Remove Windows from an HDD

Hi all. Didn't see this question anywhere else (tried Googling it and didn't get satisfying results), hope you can help. I recently built a new system, installed Windows 7 onto an SSD and took the 1TB HDD from the previous machine, in which it was the only hard drive and it wasn't partitioned. I want to know how to remove Windows 7 from the HDD (if it's even possible/reasonable), or if I need to bite the bullet and just wipe the drive. 

Thanks for any help. This is the first time I've built my own machine, so I'm still learning a lot of new stuff. 

sorry im not sure what you are asking in regards to " remove windows 7 from HDD". 

so you want to clone the drive to a different storage device? if so, clonezilla

or you want to back up the data from the old OS?

or are you trying to deactivate windows 7 from the old HDD?

Format it...

delete system32


no seriously...

Best way is to backup and wipe the drive,