How to wipe a laptop computer running on XP, Vista and 7: Use software like DBAN. You’ll have to insert it into the system tray, open it and select “scan.” Once you’ve inserted a USB or another testing device you can begin the wiping process. Be sure to use the normal booting media and follow all the prompts.
If you’re using windows 8, simply boot your operating system, go into the control panel, and then click on the storage tab. This will enable you to see all your available disks. Click on the disk that says “My Computer,” next click on “Remove here.” If you want to wipe this disk, you can click on it and then again on “Remove here.”
If you cannot remove this disk, just close it, then go to the control panel and select properties. You’ll see a recovery icon, select it and click on restore previous windows settings. Then, highlight or tick the option for “Do not erase indexing files on the destination disk” and click ok. You can now wipe your laptop if you want by repeating the above steps.