Open your registry and find the key below.

Create a new string value called 'RegDone', or modify the exisiting value, to equal '1'.

Check that the key [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Welcome\RegWiz] exists, if it doesn't then create a new key.

Next time you run Windows Update it shouldn't ask you to complete the registration process.

Key:[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion] 

Value Name: RegDone Data Type: REG_SZ Data:(0 = disabled, 1 = enabled)