Specify a folder of HTML files as the original. Convert them to JPG format, saving them to a folder named PPTOutput and create a log. All created files will use the same name as the originals but with a .jpg extension.
ConvertPPT /S "C:\HTML\*.htm" /T "C:\PPTOutput\*.jpg /C17 /L "C:\Logs\HTMLog.log"
To extend this example to convert all subfolders within C:\HTML\ simply add the /R switch. Substituting /G for the /T specification places all newly created images within the same folder as the originals.
ConvertPPT /S "C:\HTML\*.htm" /G /C17 /L "C:\Logs\HTMLLog.log /R
Note it is highly encouraged that you use the Verbose (/V) switch initially to see what the status of your conversion is.