We are disposing of some old PC's left over from a rollout. What is the best way of completely wiping the hard drive before we give them away.
Is a fdisk enough?

With the new Hipaa laws we destroy the hard drives. You can use products like Norton Utilities to do a secure wipe. Fdisk does not touch the data on the drive which allows data to be recovered and as such is not considered secure.

Carl:

If you are giving them away (do not want to physically destroy them) then there are free zero disk utilities available from all the major hard drive manufacturers websites. Usually, the zero dis utility is part of the diagnostics program. These write zeros to all sectors of the hard drive, effectively doing a low-level format and erasing them. These programs can take a while to finish, dependent on the size of the hard drive.

I use Maxtor's MAXLLF.EXE for low level formatting drives. I've been using it for about 5 years, have used it on ALL makes and models of IDE drives, and have had no problems. Download here;

http://www.xs4all.nl/~arneo/files/utilities/maxllf.exe