In short you can’t.

The problem is that even after removing all of your data – even if you remember to  remove every scrap and even after removing every single application – some of your personal information will still be left on the machine.

So don’t just take data off your PC and delete the files then sell it the data is still there!

To be safe contact a professional company such as Secure Data Recycling, there is a reason why they spend thousands of pounds on the latest equipment to facilitate the removal of old data, it is because they are experts and are contractually obliged to ensure your old data never passes to a third party.

Don’t cut corners with your personal or corporate information!