The zip file contains 3 files : 

chess.exe : program executable 
bibli.bok : opening book 
chess.bmp : logo of the program 
The engine recognizes only one command line option : hX where X is the number of megabytes that E.T.Chess should use. 
For instance, the following command line starts E.T.Chess with Winboard and let him use 64 MB : 
C:\WinBoard\winboard.exe -cp -fcp 'c:\et_chess\chess.exe h64' -scp 'c:\et_chess\chess.exe h64'