Thank you. It shouldn't be giving that error if you installed Fixt into the same location as Fallout.
What paths is fallout.cfg pointing to? Try giving it relative paths, like this:
music_path1=data\sound\music
music_path2=data\sound\music
critter_dat=critter.dat
critter_patches=data
master_dat=master.dat
master_patches=data
What paths is fallout.cfg pointing to? Try giving it relative paths, like this:
music_path1=data\sound\music
music_path2=data\sound\music
critter_dat=critter.dat
critter_patches=data
master_dat=master.dat
master_patches=data