Step#1: Download PlayRagnarokZombie Server files from here: https://www.playragnarokzombie.com/download-zombiero/
Step#2: Extract all compressed files, and make sure all of them in 1 folder. see below screen shot for your reference.
Step#3: Drag Mini-Installer files you chose to kRO clean folder you extracted. Make sure all Mini-Installer files are in the main directory.
Step#4: Replace the files in the destination. The below pop-up screen will show, and you have to click "Replace the files in the destination.
Step#4: Double click PlayRagnarokZombie.exe, and launch the client to start updating.
Step#5 : Allow the .EXE file to be opened by your anti-virus software that you have. The below screen shot shown for norton anti-virus.
Step#6: Click OK, for the message "Ragnarok.exe is changed. Press ok to restart"
Step#7: Allow last kRO folders to be updated, and then close it.
Step#8: If you accidentally clicked START, no issue, just close kRO launcher and open PlayRagnarokZombie.exe
Step#9: Click PlayRagnarokZombie.exe after you adjusted your resolution from SETUP.EXE