xdebug profiler doesn't write output files on winXP 32bit with xampp 1.7.2 because of this default setting in php.ini:
xdebug.profiler_output_name = "xdebug_profile.%R::%u"
It should be: (for example)
xdebug.profiler_output_name = "cachegrind.out.%p"
I just spend two hours on this