Well, I don't remember what the highest build number is for 2006. I think it had also to do with wich version you had. I for instance had the UK Just Trains version and it highest build number was 3092 if I recall correctly.
Patching 2006 meant, for me at least, that one had to uninstall trainz and then reïnstall and immediately patch it, that because once trainz had run the patch wouldn't work. Beside this you of course needed to switch off virus scanner, firewall, internet connection and things like virtual cd-drives, if any.
In short, if you don't need to, don't, is my advise. :hehe:
I in fact posted this because I remembered seeing that image legolistic posted a few times myself in those days.
Greetings from dusk Amsterdam,
Jan