I'm trying to help out a new client who built a site based on Drupal 6 but can't get it work quite right. I've spent a couple of hours puzzling over what's happening, but I'm not making progress, and I'm looking for ideas.

The problem: The home page contains the correct content, but has no left sidebar, where it should have an empty one. The other pages have both a left and a right sidebar, but both contain blocks that should not be there in addition to the ones that should.

The implementer tried to create an original theme, and probably put some weird stuff in the site definition to make it work right, but then abandoned the new theme and adopted Garland. The new theme is installed and enabled along with Garland, but Garland is the default. According to the Garland block definitions, the pages should be displaying correctly. None of the blocks' page-specific settings are defined, so the same blocks should appear in every page.

I know there are many ways that Drupal can be configured to display different types of content on different pages. If I were implementing a site where such variations were needed I'd define the requirements, then choose a technique that was reasonably straightforward and reasonably well adapted to my needs. But here my problem is the reverse: out of all the conceivable ways pages can be configured to display differently, which one(s) are being used, and how do I find them?

I did a significant amount of Drupal work a couple of years ago, but I haven't touched it since then. Needless to say, I've forgotten a lot. I'm spinning my wheels, and I need a way to get moving.

I wonder if there's some module that will tell me which theme is actually in effect when a given page is displayed, and which blocks it is displaying. If I knew what Drupal is doing, I think I'd be much closer to figuring out why.

Suggestions for any other types of tools, theories, or approaches are welcome, too.