YAMSQ - Multiple sites providing multiple views of same data.

Yet Another Multiple Site Question

I'm looking at rationalizing my web offerings.

Which is a fancy way of saying I maintain a handful of web sites, using various home-spun and OS site engines. This is becoming less and less manageable as time goes on. I'd like to combine them all into one site engine.

The sites are inter-related. So what I would ideally like to do is run all the sites with the same engine in the same database. But, people who come to one of my sites are looking for one thing, people coming to another are looking for another.

This is more complex than using different themes for each site. One site is providing content. I'd like visitors to that site to be greeted with the familiar site portal type interface, with the latest articles, what's new etc etc. Another site provides software, so I'd like the visitors to that site to be greeted with some brochureware style screens and downloads.

However, as people from each of the sites drill in further they tend to become interested in the other site, so having the same engine powering the same site, with the same content available (apparantly) deeper into the site the user visited would be nice.

Essentialy, it's a case of a different theme and navigation structure for each site run out of the same Drupal interface. I'm about to install a test Drupal interface to have a poke beneath the covers, but is this something that will be possible or impossible? Where would I start?

I've seen the handbook page on multiple (seperate) sites from one instance, and that I suspect won't work. I've seen posts about having one user database but different tables, would it be a case of changing the prefix on some configuration tables perhaps?

Thanks in advance.

Mike