Getting rid of old technology can be hazardous, since there's very likely sensitive data still on it. Even if it is erased and reformatted, computer hard drives contain loads of data you don't want to let outside of your firewall – e-mails, contracts, planning documents, employees' personal information, credit cards, and much more reside on these hard drives. Besides identity theft, data loss may leave you or your company liable under state laws. Deletion requires three complete rewrites on the drive before it's considered clean. But some of the newer forensic data mining technologies could potentially retrieve material that's been treated to even higher levels of erasure.
We use software that overwrites the whole drive, as the DoD recommends. If companies want to dispose of equipment that contains highly sensitive data and they don't trust simply erasing, even when that erasure is considered secure, then they can go all the way and take it to a disposal company that uses a mechanical shredder and have the drives destroyed completely.