chsh is right, people dont think, they buy their nice computer, get the software that was recommended at the time, and thats it. Little realising that updating is a constant proposition. Just the other day I was chatting to a online friend and asked when she had last updated her virus software 'Oh its been a while, I dont have the time' was the answer, she has Norton Antivurus - all you need do is connect to the net and clik the Liveupdate button, simple. Wonder how long it will be before she gets a virus....
In M$'s defense they have made it easy to get updates and patches: START > SETTINGS > WINDOWS UPDATE, and once your at the update site you can always download Windows Critical Update Notification 3.0, which tells you when an update is released - it takes too long to download though - less than a minute.
The general opinion here seems to be its the users fault, I have to agree.