Remove personal computer files before give away

I have a laptop that I am going to give to a friend. Since I have no way of knowing where it might ultimately end up, I'd like to take precautions by removing as many personal files as possible. I'd like to leave the basic software installed. What procedures should I use to get as much stuff off of it as is "reasonably possible "? Should I use some special software? Is there a 'free' or 'shareware' for this? Any comments will be appreciated.

 

Eraser works quite well for removing personal files. If it were me I would zero the drive and reinstall the OS with drivers.