Multi-Lingual site

Hi all

I have a question about performance.

My company has taken on the support of a clients web sites, one of which is multi-lingual. It is currently available in 2 languages and duplicates every page for each language. This obviously isnt good design and whilst it might be okay for the 2 languages it supports at present, they are thinking of adding another 5 or so. This would obviouly mean a lot of duplication if pages needed changing.

I've been asked to put forward a proposal for redeveloping the site keeping all its existing functionality but making it multi lingual in a more dynamic way. It is a large site with a lot of text and it is also quite complex in its functionality so i was wondering what would be the most effiecient way of adding languages?

So far i've thought of:
1) storing all language phrases and image links in a database but this would result in a huge amount of data being stored and i'm concerned about speed. though caching could improve this.
2) Using include file bracketed by a case statement checking which language has been chosen so the correct include file is added. This would be faster but means every page would have 5 or so related include files, one for each language. still duplicating things!
3) DotNet resource files but i've not made use of these before. Are they complicated and are there any problems i would need to be aware of? I dont particularily want to have to compile the site every time a new language (or change of text) is added. The more dynamic the better!
4) Manual look up to an xml file. This would be easy enough to edit on the fly but what performance issues are there with this? It would mean calling the look up method numerous times for each page for all the different phrases.

Has anyone done something similar and has some tips? Or can anyone provide any info on performance issues or ease of develpment?

Thanks for any input!!
P.

(The language is chosen by clicking a link and not by using the culture from the users browser)

Me again. Does no one have any ideas on the performance issues? Anything at all would be apreciated!
Thanks again!