Best way to erase the content of my PC to factory condition?

What’s the best way to erase the content of my computer eg all documents so that it’s basically like it was when I bought it. Is there a program?
It’s time to sell it on.
Answer #1
Depending on the OS you are using, just pop in the CD and install the OS fresh.
Answer #2
It’s Vista, don’t have the original discs, could it still be done?
Answer #3
You can download the OS, burn it on a DVD and do a fresh install.
Answer #4
THNX
I AM AN ATTENTION
Answer #5
http://www.dban.org/
Darik’s Boot and Nuke, then reinstall OS.
Answer #6
Leatherface289 replied: http://www.dban.org/
Darik's Boot and Nuke, then reinstall OS.
This is the real solution..
Answer #7
Download a w7 image, burn, and select format disk option.
Reinstall.
It’s faster than Boot and Nuke, but files may still be recovered.
Answer #8
Your computer may have a recovery partition google your make/model and see if it has and how to access it(on my acer on start up you press f11).