Free Reliable Disk Wiping Software

Hi;

My company is selling some of our old dell computers and I need to wipe the disk clean so that the data is not recoverable. I would like the disk to be reusable after wiping.

I used a piece of software called KillDisk on one of them, and I had a nightmere returning the disk to a usable state. The disk was 20Gb before,and after wiping the disk went down to 8025MB and I still can’t get it back to 20GB its a Maxtor Athena. I think the sectors are screwed.

Would like some recommendations on reliable disk wiping software…that won’t have me banging my head against the desk after.

Thanks in advance.
Jason.