1. First, click on start and type the following command to open the Windows Registry Editor

Regedit

2. Now, on the left pane, navigate to this path

Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\OSUpgrade

3. Right click on the pane on the right hand side, and create a New -> DWORD (32-bit) value.

4. Assign the following name to it. It is case sensitive, so copy and paste it as given below.

AllowOSUpgrade

5. Double click on the entry you created, and change the value to 1 in hexadecimal base. (Hexadecimal is chosen by default)