All Lessons are compressed to rar format... you just select your Class and then click on the lessons one by one...(Now it may be in downloads folder) Please copy the file to a new folder  in D drive or some where remember not keep this file in C drive.. it may be lost when format.... then select and  right the file... now  you can uncompress the file to normal power point format... it needs Rar software... you can easily download it now Download Rar.... then install the software in to your computer.... then you can uncompress the file use it