Computer support, windows 7.

[cokyy]

Well first of all this is non-ro related issue but I have a dead line so I would be really grateful if someone could answer me asap.

So my brother just got a second-handed laptop just for work but it's full with data of the previous owner. Nothing interesting, he just wants a clean wipe, however he asked me to do it and he wants to keep windows 7.
Can anyone help me? If I format the laptop he loses the OS, so I'm not really sure what I can do.
I don't think it's a genuine OS, guessing he downloaded it with a torrent.

It would be really nice if someone could help me with this.