Hi
I go with a reformat and install...
There was a news story here a few years ago, a local resident donated his old Apple computer to his church.
Some one using it discovered lewd pictures of kids who were members of the church.
He ended up in prison. I'm guessing he thought he had gotten rid of everything.
Just shows you, you can't be too careful!
Not suggesting you have any thing like that on your computer. LOL
If you really had something important that you don't want people to see, swap hard drives, they're cheap.
Mike