I am using inspiron 3542 with win 8.1, i want my laptop to reset to factory image. i do not have the backup dvd. my disk management tool is showing 4 hidden partitions, someone asked me to utilize them to restore window. I don't know the process.
Follow the instructions here to make a Bootable USB and Restore from it:
Also check the Edition here and download a .iso (just in case):