Download the file dochtm<currentversion>.zip from sourceforge. For example, if the current version is 1.1, the file to download is dochtm11.zip.
Unzip the contents of the zip file in a separate directory, say f:\dochtml.
Make sure that the file iso88591 is in the same directory as the executable.
Add the following setting to your AUTOEXEC.BAT file on the last line.
SET PATH=%PATH%;f:\dochtml