So it starts again:
Do you have M&B 1.011, you sure you downloaded .550 and .584 and put the latter into the former, with "yes to overwrite"?
And the one from a french site is the SiegePack, it's worth it.
I'll do a step by step thingy for you:
1.
.550
This should put a
Native Expansion folder into your
Modules folder.
2.
.584
Even though the link says it's .582, it's the patch for .584. All those files belong into your NE folder.
3.At this point you should download the Siege Pack, but it seems Lord Samuel has taken it down or the bandwith is exceeded. I still have it on my HDD, so if there's a problem with re-uploading I may help and I'll send him a PM.
4.
This contains a nicer texture for the Sallete Helmet and another helmet. Just follow the instructions.