What's happen, if you use global in test2.py?
x is local to test2.py.
Another possibility is to use __main__ module. But these is now depreciated.
> ##############
> #### test2.py ####
global x
> x = 'spam'
>
> #### test.py ####
> def doit():
> execfile( 'test2.py' ) # x = 'spam'
global x
> print x
>
> doit()
> ##############