Phil, that's what I used to do on my drive when deleting data no longer needed. I had a virus software package that had the same overwrite and encryption systems used by the DoD. I always settled for the 7-time pass due to time limits.
When the power supply finally went out I decided to just buy a new machine because the old one was over 5 years old and slow. I yanked the hard drive to keep and gave the chassis away.
IMHO, I wouldn't give away a machine with a hard drive still in it, just to be on the safe side. Too easy to pull them and keep or destroy it.