Computer stuck at the Installing update screen

My VISTA PC (32bit) says "Please do not power off or unplug your machine. Installing update 1 of 1" before shutdown. It has been doing so for a long time and will not shutdown. How do I fix this?

Also Windows Defender will not turn on. I get the window" Do you want to turn WD on" and i press yes and it stops there. Nothing happens and the window freezes...

Here you have MS advice:The update is not installed successfully, you receive a message, and the computer restarts when you try to install an update in Windows Vista

When you restore system from any previous checkpoint

disable all non-system services this mean make How to perform a clean boot procedure to determine whether background programs are interfering with a game or a program that you currently use

and try install hotfixes standalone versions from Microsoft Download Center