I'm running MovableType on a Windows 2000 IIS server and noticed Trackback was giving 404 errors for Trackback urls such as http://blog.tmcnet.com/cgi-bin/mt-tb.cgi/16

Most MT users use Apache running on a Linux box and MT is only "unofficially" supported on Windows IIS --- if you know where to look. I had to install ActiveState's Perl on the IIS server along with a database engine and a few other tricks.

In any event, I spent the latter half of yesterday after returning from Disney trying to get the Trackback feature to work. I found lots of other Windows IIS MovableType users experiencing the same problem. It seemed like everyone had a different solution.

This MovableType.org link suggested modifying two lines in lib/MT/Template/Context.pm from '/' to '?tb_id='

Another site stated that because I needed "mod_rewrite" (an Apache module) which doesn't come included with IIS, that I needed to download ISAPI ReWrite or an equivalent.

Well, I found the fix, and it was much simpler than I thought.

Go to this link:
movabletype.org : Support Forum

Or just read the fix here:

1) In Internet Services Manager, open the properties for the site or directory containing the MT CGI files.
2) Click on the "Home Directory" tab. Toward the bottom, there's info on the application--if none is defined, create one.
3) Click the "Configure" button for the application.
4) On the tab with the script extensions / handlers (I don't recall the exact name), look for ".cgi" and choose "Edit."
5) Make sure the checkbox labeled something like "Verify File Exists" is NOT checked.
6) Apply the changes, press OK, etc.

So simple! I hope this info helps someone with the same problem.