So Vista is going to be the disaster most suspect.
Gates got out just in time. The blame will fall on the new Chief Software Architect - Ray Ozzie.
It already is. They've been laboring 5 years to get the Vista beast out the door, while Apple is coding circles around them releasing a major OS X upgrade every year. If Steve Jobs ever comes to his senses and allows OS X to be pre-installed on major PC brands (e.g., Dell), he could give the Gates empire a run for their money.