If you’re upgrading your computer, a great way to make a little bit of extra cash could be to sell your old machine. Even if it’s a bit broken, home hardware makers on sites such as eBay would be happy to buy your old kit and use the spare parts.

Before you do anything, you’ll obviously want to take off all your precious files, such as music, videos, photos and personal documents. But most importantly, you’ll want to make sure the next owner isn’t able to recover any personal files either. To do this, you should securely wipe PC or laptop using the steps shown in the video and guide below for more. These instructions apply to Windows 7 only.

Looking to wipe your PC using Windows 10 instead? Click here.

 

Step 1: Back up

Back up everything you want to retain for use in the future. You’ll need to use an external hard drive or a server to store things.

First you need to work out how much storage space you’ll need. Assuming everything is stored on the same drive (usually the 'C' drive on a Windows computer), right-click on the drive's icon to see how many GBs are being used.

The best way to back-up your files is by transferring them in bulk onto a blank DVD or USB drive. To ensure that you don’t lose your photos and other precious files, it’s advised that you do this on a regular basis anyway.

To back-up files, simply insert your back-up device, and drag the files onto it. This will create a copy onto your back-up device.

Transferring Files

 

Step 2: How much space?

Plug in the drive you’ll be using for the backup via your USB or FireWire port and check that there’s enough space on it to store everything.

When its icon appears under My Computer, right-click it to see how much available space it has.

For convenience, you could back up online instead. BT Cloud provides 5GB storage for broadband customers, while Unlimited Broadband Extra and BT Infinity 2 subscribers get 50GB of free storage.

 

Step 3: Remove programs screenshot

 

Step 3: Remove programs

Sort out your software licences for any programs you want to continue using on the new computer.

Ideally, you’ll have stored your installation discs somewhere safe and can simply install the software on the new PC or laptop. You may need to contact the software provider to inform them that you want to transfer the licence. Check on their website for how to do so.

Uninstall any remaining programs on the PC under Control Panel, Programs, Uninstall a program.

 

Step 4: Delete screenshot

 

Step 4: Delete!

You’re now ready to delete the contents of the hard drive. Drag everything from your Documents, Pictures and Music folder into the Recycle Bin, then right-click on the Recycle Bin to delete its contents.

This alone won’t fully delete your PC’s contents, but will speed up the secure deletion process. For this, try the free Eraser tool - it overwrites deleted files several times so they cannot be recovered.

Install the Eraser software and select the files and folders you want to permanently erase. Be warned: it’s a time-consuming process. Remember to repeat the Eraser process for files on all the user accounts on your PC.

 

Step 5: Clean up screenshot

 

Step 5: Clean up

As an alternative to Eraser - and to ensure the PC has no viruses or spyware on it - erase the contents using DBAN. This will completely erase everything on the computer so the new owner has an ‘as new’ PC to use.

Download DBAN and copy it to a DVD. It’s important that you don’t unzip the file on your PC first.

Restart your PC with the DVD in place and allow DBAN to wipe your PC’s contents.

 

Step 6: Back up screenshot

 

Step 6: Reinstalling

As long as you have your original Windows operating system disk and serial number, we recommend reinstalling Windows so the new owner has a fresh PC to use.

Go to Control Panel, type in ‘reinstall Windows’ and, in the Recovery menu, choose Advanced recovery methods, then click on the Reinstall Windows option. You’ll be prompted to back up your PC first.

 

Step 7: Sign out

 

Step 7: Clear Cookies and sign out

If you won’t be reinstalling Windows before handing on your PC, make sure you delete your browsing history and clear your cookies. It's also worth making sure passwords for your email accounts have not been saved.

Go to your web mail account, Facebook and any other site at which you regularly log in and deselect any options to log you in automatically.

Your web browser may also have settings for logging in. Internet Explorer doesn’t. Check in Firefox under the Tools, Options menu for a Save Password option. In Google Chrome go to the Settings menu, click Sign in to Chrome and then Sign out and sign in as a different user.

[Read more: 8 free ways to make Windows 7 faster]