Recently oldman claimed that he could set up a machine running that other OS and use it without malware scanning. Here is proof that that is very high-risk behaviour. It has come to light that IE provides a work-around for malware-authours of two security measures implemented by M$ to enhance security. While the vulnerability has been demonstrated for several versions of IE it is also available to other applications because M$ was thoughtful enough to make some security measures optional for DLL files.
This is what happens when an OS is so complex that long lists of exceptions must be handled to do anything as simple as linking to a library. In this case an innocent user can browse to an innocent web-site that has been compromised by altering a CSS file and IE+that other OS allows arbitrary code to be executed. Now hundreds of millions of PCs need to implement a work-around to avoid creating yet another botnet of millions of PCs doing no good.