Microsoft has said that using older versions of its software opens machines to security holes that will not be fixed. They have claimed: "in practice it's impossible for us to remediate the threats that we know exist in the world today in systems that were designed in 1991, '2 and '3 and deployed in '95".
This 'push' to try and make consumers upgrade to Windows XP is a move which could be looked at suspiciously as it is clearly another drive to force people to upgrade (legally!).
They stated their future plans for the platforms saying: "We have decided that we will begrudgingly forsake certain app compatibility things when, in fact, they don't allow us to have a default configuration that opts for more security", they then went on to say: "you're just going to have to go back and pay the price".
While Windows XP and 2000 are unarguably more secure than their predecessors upgrading could involve buying a new machine for many consumers, which isn't necessarily a financial option for some.
They also said this about Longhorn: "So Longhorn, which will be the next big version of Windows -- the rights management architecture, the underlying Palladium, which is the codename for our system working with the hardware folks to create a trusted security environment within the hardware framework -- all of these things will be there".
News source: The Register