Here's a quick fix, but untested as I haven't got access to Wordpress at the moment in order to check.

Within Wordpress go to your permalink settings page and activate the custom permalink option. Enter your preferred permalink. In your case something similar to /online/%post_id%. Save the entry.

Now return to the conversion process and try again. The tag %post_id% will/should force the original Wordpress post_id to be retained.

For further reference re - custom permalinks check here.

I hope this helps and I'll check it out myself when I've got access to Wordpress over the weekend.

ps. What I would recommend is, if you can, upgrade to Wordpress 2.5, then use the latest converter, at this time Version 1.04, as there are more options available and fixes things that weren't quite right in the pre Wordpress 2.5 version. All development work on the pre Wordpress 2.5 version has stopped.

I've just tested the above where the custom structure is

and the permalinks are correctly imported.

The Drupal URL's will appear like:

Turn on Clean URL's and the Drupal URL will be:

The ending bit %3Fp%3D371 is caused by the ?p= part but as you can see includes the post_id number 371. Granted, this is ugly and not what you would want and I'm not sure how to correctly convert the ?p= part. Lets call that one a 'spanner in the works'.

You do have options. If your custom structure is

then your Drupal URL's will be similar to (with Clean URL's enabled):

Granted, it doesn't include the ?p= part but that can be addressed with a redirect in your .htaccess file. In your .htaccess file it's simply a matter of creating a Rewritecond and Rewriterule (two lines of code) to redirect all traffic looking for the old URL to point to the new style url.

Hope this helps.