We format hard drives to prepare it so that the operating system (e.g. Windows XP) knows how to use it. Different operating systems use different file formats. Formatting also deletes everything on the drive. As for integrity checking, you could do basic error-checking by right-clicking on My Computer -> Properties -> Tools -> click Check Now. Explore the options available there. There are more advanced tools available for download or purchase for more comprehensive hard drive maintainance.