It is easy to dismiss the cost of licensing for an OS as minor when you buy a new piece of hardware to run it. Usually on the grand scale of your hardware purchase the OS cost is just a small percentage of the overall spend and that worked wonders for Microsoft selling Windows, HP selling HP-UX and IBM with AIX - no one cares, but everybody pays. Well, virtualization topping all IT agendas pretty much all over the place, the OS tax will be becoming a whole lot harder to ignore. For a simple reason that the more OS images you cram into your favorite piece of hardware, the harder it becomes to ignore the OS licensing costs. In the case of Microsoft Windows it will be impossible to ignore - the Microsoft Windows licensing costs are so high that running just a few virtualized instances of Windows on the same entry level box will make cost of OS licensing higher than the cost of hardware! Well, Microsoft has been overcharging for essentially an inferior product for a long time and at some stage people should wake to it, but this is a topic for a different conversation. What is more important is that with virtualization becoming more popular the old ways of licensing operating systems per instance may become obsolete and if the OS vendors do not wake to it, they may find there market share rapidly declining. At the very least Solaris and Linux should be putting more pressure on the vendors that cling to the old ways of licensing their OS products per instance.