about user accounts

That's not a very good idea, for a lotta reasons. In fact, its best to not have the ADMIN account available from the login screen unless Ctrl+Alt+Del is pressed at the welcome screen. You should configure a user account other than for ADMIN for yourself. Configure that account as within the Administrator group, granting it fiull permissions, then configure it to require a password on return from screensaver or return from standby, set your screensaver and/or standby configuration to whatever time period seems convenient for you, and you should be just fine as far as limiting unauthorized use or access. Any number of programs exist which will enable you further to password-protect any folders you deem critical; some are free, some you have to buy - google "Password Protect Folders" and do some research. You can always (and should) limit the permissions of the Guest account, preventing any user on that account from modifying files or installing/uninstalling applications. With that setup, only you, or someone with your password, can access your Windows logon account, and if you password-protect your critical folders, using a different password, of course, you've put up yet another wall between your stuff and anybody but you.