When a browser, that is a program running on top of the operating system, and NOT the operating system itself, for those outside the planet, connects to a website which is slow in responding, such as NPR a few minutes ago for me, when connecting to something called World Cafe, the whole computer freezes under Win 7, and earlier, until the website responds, Ctrl+Alt+Del has no effect. This is fugging unacceptable in 2013, problems of this type had been solved in computer operating systems 30 years ago if not earlier!
I've started to run Task Manager in the background to allow me to shut down the programs, in XP.