I know windows has a built in tool, but aside from that.
David: Various options here:
I would to a factory restore – there will be an option the laptop on the then download ccleaner and use the wipe free space option, alternatively make a USB recovery drive, use DBAN http://www.dban.org to securely wipe the drive and then reinstall the operating system from the recovery USB
If you want to make sure absolutely nothing is retrievable, then use the following program. This is what Hillary Clinton's IT people used to clean her server. As you know – if you follow the news – none of that information was retrievable, even by the FBI
Well, if you are donating it then you are giving it away for free.
If you want to give it away or sell it as a working device with an operating system on it and loose your personal information then you lose the personal information;
It is little time wasting job, but its better to erase your hard disk by making a windows installation. don't forget to format your drive while installing.
DBAN is free and effective.
You will need to do a clean install from a Windows disk or restore discs after you run it, but all your files will be wiped.
Look on your datas, all wanted you is other user.