USMT 4.0 vs USMT 3.0

Right!!
A big load of my mind...
USMT 4.0 does only work in these Scenarios

WIN7 to WIN7
Vista to Vista
Vista to WIN7
Win7 to Vista
WinXP to Vista
WinXP to WIN7

However it does not work for:
Win XP to Win XP
you have to create and use a USMT 3.0 Package for that!!