On the Which type of installation do you want? page, click Custom.On the Please read the license terms page, if you accept the license terms, click I accept the license terms, and then click Next.On the Install Windows page, enter your language and other preferences, and then click Next.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. To change the boot order, you'll generally press F12 immediately after you turn on 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. Turn on your PC so that Windows starts normally, insert the Windows 10 DVD or USB flash drive, and then shut down your PC.Please backup system data before upgrading to Windows 10.If you bought Windows 7 SP1 or Windows 8.1 on DVD or created a DVD or USB flash drive when you purchased and downloaded Windows 10, follow these steps to perform a clean installation.