Carl,
Adding to details from John and Ben...
The .reg extension just makes it able to install if double clicked. The name is not important - a self documenting name is highly recommended since the contents is difficult to read since the column headings are hex values (to support multi-byte attibute names), so NX_X.Y_ANAV_for_Department_Z_rev_1.reg might be helpful.
The ANAV info for native NX and TC managed are stored in the same registry entry. NX just ignores the columns that are only relevant to TC when running native mode.
The column titles, content, width, and visibility are stored in the registry so if the original machine that exported the reg file had the additional columns, the receiving machine that used the reg file would not need anything defined - the identical columns, titles, order, widths would be created from the imported reg file.
HTH, Joe