Mainly due to Microsoft making sure the security is set. Well we can thank all the hackers over the years for that...

EDIT: I should add this really doesn't bother me all that much...it means I have more time now before I buy a new computer. I would rahter wait until later 2007 anyways so they can get out a Service Pack for any bugs...hehehe. But I am looking forward to a new Operating System. From what I understand is you will need a whole new animal of video cards to get High-Def out of Vista. Other more Geeky people can explain that better then I.