Dazz_G
Emperor
Chasebolt - Dazz G didn't seam to have any problems opening the 1.74 file for a different game that I sent him. You should ask him for some advice on opening the file. I will also resend to you just in case something went wrong there.
If only ...
Firaxis have a lot to answer for with BtS 3.13

Chas cannot open the file with 1.61 ... not compatible.
His 1.74 is no longer compatible either if he has patched BtS to 3.13 as this ingenious patch alters the core Civ4 program meaning his 1.74 is no longer standard 1.74.
I uninstalled BtS to get rid of the patch but this rendered Civ4 inoperable, hence the length of time it took me to play NITF.
Assuming i'm right about Chas's problem, the only way I see to fix it is to pretty much uninstall everything, install Civ4 and patch to 1.74, copy and paste the whole folder, then install BtS, patching to 3.13 if you wish. This will also alter your original Civ4 install but not the copy'n'paste version.