I'm trying to wipe a 2TB hard drive ready for sale. I was told to zero it out with 7 passes so it would be secure and no-one would be able to retrieve my information. But I'm struggling to find a program that will perform one pass in less than 24 hours let alone 7 passes. I was just wondering out of interest and maybe for some fun, would it be secure to overwrite the data and occupy the empty space with 2000 1GB films?
If you just want to wipe the disk, ensure it's the only disk in the system and then hit it with Darik's Boot and Nuke.
There's no certainty, there's only confidence...
Completely overwriting a drive several times would make it difficult to recover the original data, but not necessarily absolutely impossible - it depends on whether it's a couple of home movies & some bank details, or you had plans to blow up somebody's embassy as to whether the effort required would be worth it.
Re-Writing all the data 7 times will take time - about 7 times more time than filling the drive with irrelevant date once, yet ought to be more 'random' than filling it with files.
If you're really paranoid, the only way to absolutely securely erase a drive is with a large hammer.