If the system does not automatically prompt to upgrade Win8.1 how to manually upgrade

solution:
When you are officially purchased genuine or have an ISO CD image file already in Windows 8.1. This document will take you step by step through a CD (mirror) installation to upgrade to Windows 8.1. The disc image used can be obtained from a Microsoft MSDN subscription account or a TechNet subscription account or a third party website.
The test hardware of this document is Lenovo IdeaPad Y400 notebook, the hardware configuration is Intel I5 3210M, 4G memory, 1TB hard disk, and the test ISO CD image file used is Microsoft MSDN subscription account download. All of the following test screens and test times are measured on this hardware platform and are for reference only.
The specific installation upgrade method can refer to the following steps. Due to the upgrade installation of the system, computer settings, data changes or loss may be caused. It is recommended that you do a backup of your personal data before the actual operation.
1. Double-click the left mouse button to select the ISO CD image to be extracted to the folder;

2. Open the newly unzipped folder and double-click the “setup” program in the folder;
< Br>3. Pop-up user account control, click “Yes>;

4. The program starts to initialize, please wait a moment;

5. Click “No, thank you ”, then click “Next”;

6. Enter the 25-digit product key and click Next.

7. Check first > I accept the license terms” , then click "Accept" button;

8. Default selection “Keep Windows settings, personal files and applications", and then click “Next”;

9 Please wait a moment;

10. Click “Install">;

11. Waiting for installation, this process lasts about 6 minutes;

12. The computer starts to restart The whole process is restarted 4 times for about 24 minutes;

13. Click “Use Quick Settings 

14. In the login account interface, you can choose to log in with your Microsoft account. (The account is a pre-registered Microsoft Personal email), you can also choose to log in using your local account. If you don't have a Microsoft account or just want to use a local account, click “Create a new account";

15. Then click “Continue to use my existing account 
< Br>16. The computer appears in turn "Hello", wait a moment;

17. The screen will display a colorful background, complete the remaining application installation, this process lasts about 4 minutes;

18. At this point, the Windows 8.1 upgrade installation is complete.