To reformat a laptop, boot off of installation media such as a USB drive or a DVD. Before attempting the format, ensure you create a backup of all essential data currently residing on the hard drive. Additionally, create a disk with all the necessary drivers for your laptop.
To format using a Windows installation disk, insert the bootable installation disk into the computer, restart the laptop, and enter the BIOS settings. Change the necessary settings to boot from your Windows installation disk, save the changes, and restart the laptop.
Once the laptop boots from the disk, select your language, accept the license terms, and select the Custom (Advanced) installation type. When the list with the names and letters of your drives appears, select the drive you wish to format, click Drive Options (Advanced), and select Format. Once the formatting is complete, click Next to start the installation of a fresh copy of Windows.
To format a drive from within the normal Windows mode, search for the Disk Management tool, open it, right-click the partition you wish to format, and click Format. Once the Format dialog window opens, click OK, and click OK again. When using the Disk Management tool, you can't format the partition with the Windows installation or a partition currently in use.