<A target="_blank" href="http://arstechnica.com/microsoft/news/2009/05/r2e-microsoft-intel-goof-up-windows-7s-xp-mode.ars">The Windows 7 "XP Mode"</A> looked good on paper. But, when people started trying it out, they ran into problems. It seems the feature only works on either Intel's VT or AMD's AMD-V chips - but not even all of them.