Welcome gwhizz1122
You sure you installed 1.0? If you bought a budget version of the game it might very well be 1.4 out-of-the box. That will give you the same message when trying to patch.
If not try to remove every mention of SHIII on your computer (there is also a SH III folder somewhere in documents and setting if using XP) and make sure that you d/l the right version of the patch, correctly mentioned as US or EMEA. Then try a fresh install and patch it again.
I'm pretty sure Neptune is on your side
After you get used to stock 1.4 be sure to give GWX a try....
Gute Jagd!