Actually my problem is to log in for the PC i.e i want to disable some activities like a person should not access date and time
There are many ways to limit some tasks and functions. If one has physical access then it is rather difficult to prevent any changes. Simple people might be stopped by registry edits or policy settings or user privileges. A standard limited user can't change time in a normal install.
1/3 of highway deaths are caused by drunks. The rest are by people who can't drive any better than a drunk.