How can you use mod hacks in sonic adventure dx demo

alright so you download a mod and:

1.Backup the system folder it should be on C:/programfiles/sega/sonicadvneturedx/system or something like that
2.Copy the files that you downloaded (copy the mod) into system folder (not backup of system).
3.Enjoy mod

AND don't blame me if you forget to backup files and you loste em.