The following is provided by The SysOp of Tecmecca BBS

Tips for creating your own custom install 

Extract the files into an empty directory by typing excaltrm.exe /x from a DOS prompt.
This will put all of the installation files in one place. knowing where they go in a norma
installation is essential.

Copy and additional files (cilent side plug-ins, images, etc) that you want to include in the
same directory. By doing a fresh install and then connecting to download the extras, I was
able to easily pull out just the files I wanted to include from the client directory.

Run the install creator. The wizard will get you started but more must be done to get
everything in the right place, so don't build until you manually configure file attribites for the
system files, fonts, etc. This will take some figuring and a couple of tries before youget it right.

Test trhe build on a clean system. If you don't, things may appear to work that actually won't 
on a true fresh installtion. Pay special attention to system files, fonts, and sounds. For example,
I created a sounds.reg file exporting the registry entry created by a normal excaltrm install.
Then I used the Install Creator option to automatically register that file. Without registry entries,
the wolcome, goodbye and file done wav's won't work.