Never mind, I seem to have resolved my problem - I initially installed the FIXIT patch into a separate folder within Fallout, not the actual fallout folder itself - although thanks for the quick reply!
One further question - I have installed Fallout within Program Files, and am using Windows...
I've just purchased Fallout 1 and 2 from Steam, and installed Fallout 1 Fixit, however when I try and run the new FalloutW application, I get the following error message:
"Could not find the master datafile. Please make sure the FALLOUT CD is in the drive and that you are running FALLOUT from...