I cannot upgrade Boot Camp 3.3 to 5.1.5621

I have downloaded the 5.1.5621 new version of Boot Camp but it refuses to open. When I go to boot camp, there is no provision for upgrading either. If I try to open this update on OS X, it says I should go to Windows and open Boot Camp, but this does not work either.

Why can't there be a simple way to upgrade ? Beats me.

Why I want to do this ? : It seems to me that upgrading Boot Camp is the only way I could obtain the latest drivers I need, because I am constantly advised that Intel(R) Turbo boost Technology driver has a problem, also Intel(R)5 Series chipset family 3B36 needs reinstalling and, finally, also 3B3B.

Could someone please advise the way to proceedwith this upgrade ? Thanks