You can restrict Users to access Windows Update.
To do so , navigate to :

-HKEY_CURRENT_USER\Software\Microsoft\Windows
\CurrentVersion\Policies\Explorer\


Create or mofify here in the right pane the entry :


NoWindowsUpdate


If you need to create it do a right click in the right pane , new ,
REG_DWORD [DWord Value] and name it as above.

Doubleclick the entry and set it's value to 1.
To enable it delete the entry or set it's value to 0 to disable it.


Note:
I did not test this entry as I do not access Windows Update anyway.
This is valid for the current logged in user,where you edit this.