Are you running a tormach version? The powerfeed wizard has an init.m1s file in the folder under Addons\PowerFeedXY. That file has c:\mach3\ hard coded in it. That really should be a test for the program folder, not hard coded.
If you are running with the mach3.exe in a different folder edit the init.m1s file.
I will see if I can make a proper fix to that.