I'm going to create a website using Wordpress static pages feature. It's going to have a menu for all the created pages.

A blog is going to be created as well. This blog has a completely different layout/menu from the main site, but within the same domain: "http://www.domain.com" is the website url, and "http://www.domain.com/blog/" is the blog url.

I was thinking of installing two different Wordpress instances: /var/www/public_html/ and /var/www/public_html/blog/. Although it's a simple solution, users are going to be duplicated: if you change password in one system, you need to change in the other.

So, I would like to know from you which other approaches are possible: create a "dynamic" theme (call a theme when in root domain, another whern /blog - dont even know if this is possible), or for example a plugin to syncronize users from both instances?

Does Wordpress MU solve this problem for me?

Thanks!