Here are three zip files that will enable you to set up automatic (daily if you like) updates in ACP for the Minor Planet Center's minor planet and comet databases. I've been running this automatically for 10 months on daily basis without a hitch. It's unattended updating, set up at a frequency and time of your choosing, requiring no user intervention, and silently disappearing when the processes finish.
Unzip the files and follow along through the instructions. A warning, though - if you have trouble with permissions for writing into the MPCCOMET and MPCORB folders, this automatic process will also fail. There is no special permission-skipping capability here. (This has been a long-standing issue for a few users, particularly for Windows 7, and Bob is working on how to resolve this issue.)
Let me know how it goes.
EDIT: Replaced the original Put_in_MPCCOMET_Folder.zip with a new one that has an updated MakeCometDB_noEcho.wsf file. This new file enables ACP to find comets with "A/" Names