Windows won't restart or shutdown and can't install software

As the title suggests basically.



I cant shutdown my system through the start bar or through the task manager
options. I always have to hold the button on the front of the tower to shut
down.



I also can't install any software. When I click an .exe file or try to
download flash for youtube for example nothing happens. If I go into task
manager I can see there is always an exe in there but nothing is happening
basically.

I've gone through Microsoft updates and downloaded everything I can find but
nothing changes. i can download and install updates from Microsoft though.



Any suggestions.



Thanks



Baz

.