How to perform a clean installation of Windows 8

 You can perform a clean installation of Windows 8—which typically means formatting your hard drive before installing Windows—using upgrade media, but you need use the Windows 8 Setup program to reformat your drive. You also must have a previous version of Windows running on the PC—you can't install on a bare drive.

To perform a clean installation using a DVD or USB flash drive

If you bought Windows 8 on DVD or created a DVD or USB flash drive when you downloaded Windows 8, follow these steps to perform a clean installation.

1. Turn on your PC so that Windows starts normally, insert the Windows 8 DVD or USB flash drive, and then shut down your PC.
2. Restart your PC.
   If you restart your PC and your current version of Windows starts, you might have to change the boot order in your PC's BIOS settings so that your PC boots from the media. To get instructions on changing the boot order for your PC, check the documentation that came with your PC or go to the manufacturer's website.
   To change the boot order, you'll generally press a combination of keys (such as F2, F12, Delete, Esc) immediately after you turn on your PC. If your current version of Windows still starts, try again by waiting until Windows asks you to sign in, and then restart your PC again.
   
   
3. On the Install Windows page, enter your language and other preferences, and then click Next. 
   
   
4. On the Please read the license terms page, if you accept the license terms, click I accept the license terms, and then click Next. 
   
   
5. On the Which type of installation do you want? page, click Custom. 
   
   
6. On the Where do you want to install Windows? page, click Drive options (advanced). 
   
   
7. Click the partition that you want to change, click the formatting option you want to perform, and then follow the instructions.
   
   
8. When you've finished formatting, click Next. 
   
   
9. Follow the instructions to finish installing Windows 8.