How to Upgrade Service Pack 3

• Open run command from start menu, type regedit 

and navigate to...

• HKEY_LOCAL_MAchine
• System
• CurrentControlSet
• Control
• Windows

On the right side...

• Right click CSDVersion
• Select Modify
• in Value data type 300 to make it SP3
• (type 100 to make it SP1,type 200 to make it SP2)

• Click OK and close everything
• Reboot, and done!