[jjcm]

It seems naive that you assume that banning Windows would decrease the rate of successful malicious attacks on machines. Every piece of software has holes - the largest of which is the user. If everyone in the EU switched off of Windows, you'd just have a large percentage of the population using linux or OSX without understanding how security works on those systems (many of whom would gladly enter their root password to install a spyware program, so long as they can keep playing farmville or whatever it promises to do).