Is Your Hard Drive Really Clean

Today, I just found out that that 74% of discarded PC hard drives contain private data that can be easily read and recovered even if the drive has been reformatted? I know there is some kind of software to retrieve deleted or re-formatted drives. Due to this, software developers have develop a software that will Wipe hard drive clean. It will permanently erase files, pictures, documents, credit card info, bank statements, passwords and more.