What is the difference between the Unix and Windows XP interface?
If you are asking about the graphical interface, windows XP
comes with just 1 interface, and it can be customized to a point,
but that is somewhat limited.
Unix comes with multiple graphical desktop managers, not just
one. Users can pick and choose which environment is best for them.
With Windows, the choice is already made for the user.
Handling of icons and desktops are very different in Unix and
Windows. The list would be too long to detail in this answer.