> Do like the readme that came with the diff file says.
>
> copy area51.chd to a seperate directory
> rename area51.chd to area51a.chd
> unzup area51tw_chd_diff.zip to the same directory
> unzip the chdman.zip to the same directory
> type chdman -merge area51a.chd area51tw_diff.chd area51.chd
>
> CMP 3.31a will now be happy! :-)
>

Thanks djspeedy. The file I got off a.b.e.m. did not have a readme.

Thanks again.