Hi
It's a good idea to make sure your computer is clean when you give it away.
We had a case here that involved a man (someone who worked at the same ad agency I did many years ago) giving his old computer to his church. That was a nice thing to do, what could go wrong with that?
The problem was that when the people at the church went through it, there was stuff left on it that ended up sending him to prison.
But to get to your question, I just do a clean install of Windows as everyone else has said.
There is software that completely erases all data on the drive, something that a format doesn't really do.
But unless your computer is filled with Top Secret information from the CIA you probably don't have to worry about it. LOL
How to Completely Erase a Hard Drive | PCWorld
Mike