Hey I had this problem and it was very irritating... I couldnt even complete the humungous installation as it said that it couldn't write the "master.dat" file. I explored the cd and discovered that the master.dat file and critters.dat file were read only and couldnt be changed... so I had to manually copy the entire contents of the cd to my computer... then run the setup again (choosing the directory where i had already copied all the files to) chose the smallest installation and voila! it created all the registry files and shortcuts i needed in about 2 seconds! got round the nasty "master.dat" error wonderfully... i hope this is useful to some people as fallout is so freakin great! gotta share the love
p.s. if you wanna use the patch then do as instructed above, then install the patch and then do the SMALL setup again... from my experience doing the huge install overwrites the master.dat and critter.dat files with copies of no size...i.e. says they are 0kb in size
