A-V-8R - for those special moments when you want to shut down almost everything as you mentioned, use EndItAll, a very neat little piece of freeware by the great Neil Rubenking.
Cleanly closes everything unessential to Windows (customisable) so you don't have to give 'em the three-fingered-salute one by one. Get it at
http://www.pcmag.com/article2/0,4149,697,00.asp or just search for EndItAll with Google.
I'm using McAfee with no hassles meself.