If your SP3 update freezes after going thru most. Just wait for some time 15 Mts., Then Use Task-Manager. (Task Bar - Right Click and see). Cntrl + Alt + Delete Just Once, Quick, like in old days pops up Task Manager.

Now See for activity in update or sp3, either way after some time; End the "sp3" process line and all/any "update" process lines. The Frozen window goes away. Now Boot, Reset or Turn Off/Turn On your System. Wait-n-Watch it should go through now and complete job automatically.