Your best bet would be Ubuntu, PCLinuxOS or even PC-BSD. the latter of the 3 is more Unix based but it has the KDE interface which is almost like a exact clone of XP.
I have personally used all 3, and you know what type of Windows person i am, and of all i would use PC-BSD if it had better support for my hardware. PCLinuxOS is a great Distro as well. Another KDE based Distro it is easy to use and is easy to work with.
Ubuntu is the XP of the Linux world as everyone trying to escape Windows flocked there. Simple to use and uses the Gnome interface.
Ubuntu would be the easiest to get support with. PCLinuxOS i had few issues with. PC-BSD Saxon knows very well.