It's a simple little freeware tool that locks your system after a set time or if you need to leave it unattended. PC Access Guard's configuration interface merely offers three options and a password field. You won't need a manual for this program. Using the tray icon pull-down menu, you simply set the app to start guarding your system.
Any key press or mouse click sets off the alarm. There is no other notification that a password must be typed immediately. We would have preferred a dialog box requesting the password. Nevertheless, you simply type in the password and the tray icon stops flashing red. That's your only indication you've entered the correct password. Fail and the program shuts down your system. Of course, you can simply start it again. An option to start monitoring on system boot-up is available, though.
Oddly, uninstalling this program does not disable it immediately, so it's clearly leaving some traces behind after you remove it. It's not perfect, but at no cost, PC Access Guard does a decent job keeping others from accessing your system.