Preparing laptops to sell

[kration]

I'm looking to get rid of three laptops on a popular auction site, but I'm wondering how best to prepare them so my personal data, files etc isn't recoverable.

I've got two with Windows 10, and one with Windows Vista.

I've googled it but it's all a bit confusing. Any advice is much appreciated.

 

[MiSJAH]

DBAN.

 

[kration]

DBAN.

That looks to do the job.

But I've looked through the link and again I'm a bit confused about how to wipe the laptop but sell it with the OS in place?