Oh, BS, Jonty. Windows was forced to take the steps that Apple took a long time ago to match the security of UNIX™ that was built into OSX from the first. Quit trying to rewrite history. Apple took those steps back in 2001 when it dumped Mac-OS9 and lower and even THAT was more secure than Windows was then. It's been Microsoft that has been playing catch up.
Windows will always be more vulnerable to viruses, due to being a more open program than Apple. I can’t just go pull a program off the shelf and load it onto Apple, as I can with Windows.
However, as one computer teacher told me, that is the tradeoff with using a more open system, like Windows. On the plus side, it’s been years since I caught a virus, so it would appear that Microsoft has learned a lot.