Trying to explain this better, I hope.
Ok, I have been digging around in these Forums for a few days (well ok, today), trying to figure out how to set the default language to Norwegian.

Now, I have been working with Joomla for a few years now, so I know my way around.
However, I have just started a new site for testing purposes, and this is on the new Joomla 1.6.3 platform.

I tried installing the Norwegian language pack, and yes, it installed easy.
But despite front end (site) was set to Norwegian etc, the frontend was still showing English.
So I looked here of course, and see that loads of people are having the same problem. So I thought, hm, solution MUST be here somewhere...

After trying all sorts of things, I stumbled on a link with the English language install. Well, I already had everything installed and working in English, so what's the point of that?
And I didn't see anywhere that it's different...

Reading the documentation, Page 144, explained exactly what I had done, so what's the problem?
However, I still downloaded the English file. Opened it, and saw that the ZIP is different to the Norwegian pack I had.
Not sure why, but I recon this IS the main problem people are having.
People are generally doing everything as they should for 1.5, which doesn't work on 1.6.
(On aftersight, I see that Krileon is actually saying this, I just didn't understand it... and it seems others are having the same problem. -also, strange this guy remains so relaxed when faced with the same questions over and over...)

So, simple advice for people having trouble with this, download that Base English language file here .
Then open it, and at least for the Norwegian files, I could "almost" just rename the old language file, to the new one.
In short, rename the file that previously was called: norwegian.php to language.php and just stick it into that Folder you just downloaded!
Follow the same instruction for the other files, and just leave all other files as they are (basically).

No, you're not quite finished yet...
Then you re-zip all of that, in my case to: norwegian_nb-NO.zip
The actual file name on install get positioned according to the XML file where you have the name in the <name TAG>, so just make that tag nb-NO (or whatever your language is).

NOW you can install it!