Hi Pete, all,

At least in theory (*), this all ought to be reasonably simple :

Extras... Asteroid/Comet Options... Add MPC comets/asteroids
should get you a "Guide help" screen that explains about the Minor
Planet Center and the IMCCE, and their role in providing orbital
elements for comets. In the middle of that screen is red text
saying "Click to download updated comet data and add it to Guide".

When you do that, it will collect Soft02Cmt.txt from the Minor
Planet Center and rename it to 'soft02cm.txt'. You _can_ do this
manually, as has been described by others on this list, and the
effect will be exactly the same.

Clicking on that will _also_ get the latest comet data from the
IMCCE. Sadly, they haven't updated that for over a year. I may
have to just go ahead and compute those orbits myself (which I may
have to do anyway for another project I'm working on.)

All of this _only affects comets_. Asteroids are an entirely
separate matter. To update those, you need to get

http://www.minorplanetcenter.net/iau/MPCORB/MPCORB.DAT.gz

and put its contents (MPCORB.DAT) into your Guide folder. You
also have to make sure that, in Extras... Asteroid/Comet Options,
you've checked the "Use MPCORB" box. (If you don't do that,
Guide will use some elements that are built onto its DVD.)

-- Bill

(*) "In theory, theory and practice are the same thing. In practice,
they aren't."