What gets saved when you export a WordPress blog? I know the format of the export file is XML and that all posts, pages, categories and authors are exported. See:
http://support.wordpress.com/moving-a-blog/
Not sure if files, sidebar settings, themes or roles can be exported…. There are tools that exist to migrate WordPress blog to other platforms, but not all or perhaps any of them will migrate files…
WordPress to Drupal
There are two main modules for migrating WordPress content to Drupal, see:
http://drupal.org/project/wp2drupal
http://drupal.org/project/wordpress_import/
WP2Drupal interacts directly with the database, whereas WordPress_Import uses the WXR export file. It is not clear whether these migration modules also migrate WordPress files. There is Drupal code out there for migrating files on a remote server to Drupal, see:
http://bensangeorge.com/2009/06/drupal-bits-migrating-remote-files-in-drupal/
It also looks like Drupal is working on a migration framework, see:
http://drupal.org/project/migrate