Source -Program compatibility in Windows 7 is significantly improved over Windows Vista and aided further by the support for XP Mode, a vitual machine running programs in Windows XP on your Windows 7 desktop.
The problem with XP mode though is that it requires hardware virtualisation support on the motherboard, and a great many business PCs simply don’t have support for this.
Microsoft pushing for ‘green-lit’ Windows 7 Applications | Windows 7 News