Remember the MSblast virus? You couldnt install the patch unless you had
Servce Pack One installed. Big deal? Unless you had a pirated copy of
Windows XP, using the widely circulated serial number, the service pack
wouldnt install hence you couldnt patch yourself against the MSblast
virus. Of course it wasnt long before there was an application that made
it possible for you to change your XP serial number and solve the issue.
Mr Gates seems keen to implement a system where you would pay for the
privilege of protecting yourself against viruii, aimed at Windows OS, so
it makes sense he would then create viruii. Without virii there would be
no need for an update/patch service for Windows (apart from the growing
list of Windows OS bugs).
I cant think of any other examples similar to the MSblast virus but I'm
sure there'd be other instances of not being able to protect yourself
against a virus without jumping through another M$ hoop.