Help With Data Destruction/Hard Disk Formating

[Valo]

I have just upgraded the storage on my RAID5 array and have 4x 500GB hard disks that I want to sell on.
Before I sell them on I want to obviously make sure that each disk has been thoroughly formatted (zeroed?) and has been error checked, I'm looking for preferably free software that can do both tasks rather than trusting the basic Windows drive tools.

Drives will be connected to my system via my Sharkoon SATA-USB cradle.

 

[IAmATeaf]

I always use KillDisk, the free version allows only a single pattern write but should do the trick. No idea if it'll work via the cradle though.

 

[Valo]

I always use KillDisk, the free version allows only a single pattern write but should do the trick. No idea if it'll work via the cradle though.

That looks like exactly what I'm looking for!

Cheers