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.