Okay, a bunch of people have hit this page through searches on how to remove the W32/Nimda worm.
So here's the scoop: McAfee has released a free Nimda cleaner. I haven't had to use it, because my systems are not infected. So if someone uses it, please email me and let me know if it does in fact do the job, so I can update this entry with that information.
Update: I'm told there's an updated version of the free Nimda cleaner, which I'm assured does in fact work.