Mervyn,
I had another user who reported that they didn't have this file ("Consist-preamble.dat") That file is supplied with the full install of Activity Generator. I suggest you use the download link and re-install Activity Generator (you might want to go to Control Panel then Add/Remove Programs and UNINSTALL Activity Generator first).
Also as Don points out, if you're running his template, you should be using SwitchList Generator classic which also comes with the full install. If you're running Norm Beveridge's template however you should use Activity Generator 3 or later.
If you need to reinstall Activity Generator and don't have the link please email me directly at SteveDavis@skylinecomputing.com and I will send it to you.
Thanks,
Steve