You will not be able to add "Local Users and Groups" to a Windows 7 Home Premium since it's not available for that edition.
Are you getting this error when you try to open your
C:\Users\HoSoon folder? Does it give you a prompt to click on
Allow to then be able to open it?
If this has just recently started, then you may be able to fix it by doing a
system restore using a restore point dated before this started.