KidSafe is a computer-locking application designed to keep young children from messing anything up.
Ever had your desktop icons scrambled or your Word document deleted by a little kid? KidSafe's for you.

KidSafe will launch a full-screen window that hides the entire desktop, TaskBar, etc. Because the window is blank (except for the unlock entry box; see below for details), clicking it won't have any effect. Small children, who generally enjoy clicking the mouse, can click all they like without damaging anything.
If the appropriate option is set, KidSafe also prevent the system from being shutdown - even if a small child presses the power button, the system won't shut down.

If the appropriate options are set, KidSafe can disable all of the system keys - the Windo
ws key, a combination of the Windows key and any other key, Alt-Tab, Alt-Escape, Ctrl-Escape, and Ctrl-Alt-Delete. This can be very useful, especially if a small kid keeps accidentally opening the Start Menu and selecting items in it: just disable the Windows key and the Ctrl-Escape key combination, and voila! No more Start Menu.

Setting up KidSafe
Due to popular demand, KidSafe has had a graphical interface for editing its options since version 3.6.0.0; however, it's very difficult to accidentally turn a setting on.
Settings can't be changed without entering the unlock text (unless there's no unlock text set), and the preference entry fields are almost impossible to change without meaning to - the entry fields are textboxes, not multiple-choice options, and the textboxes are carefully set up so incorrect input turns the given option back off.
Each setting starts with a default of off, or NO (except for the "treat unlock text boxes as password entry fields" option, which is on by default as of version 3.6.0.0), and YES must be entered to turn the setting on. Entering anything other than YES will automatically turn the setting back off.
Also, KidSafe's feature disabling is only temporary - even if KidSafe crashes, none of the disabled features will stay disabled. The worst that can happen is that you might need to reboot your computer to restore everything the way it had been before. Even the Task Manager will be restored - unlike some applications, KidSafe's blocking of the Task Manager is only temporary. Even if KidSafe crashes, the Task Manager won't stay locked.

Closing KidSafe is very easy - just type the unlock text into the unlock-box in the middle of the window, then hit ENTER or press the OK button. KidSafe will compare the text you typed to the real unlock text (just in case a little kid might be typing in the unlock textbox), and close if the two entries match (the text comparison is case-sensitive, so an unlock text of "PASSWORD" won't match an entry of "password" in the unlock textbox). If they don't match, KidSafe will put up an error dialog; close it by hitting the "OK" button. Once the two entries match, KidSafe will close and all of its changes will be undone.
(In Screensaver mode or Hotkey mode, the "OK" button is replaced by two other buttons, "Hide" and "Close")
If there's no unlock text in the preferences file, or the preferences file doesn't exist, KidSafe will automatically close - this is a precaution designed to avoid trapping users in the KidSafe dialog without a way to exit.

Manually editing the KidSafe configuration file
KidSafe's configuration file is fairly simple to edit manually as well (except for the unlock text); there are only a handful of values you can edit, and almost all of the values are simple true/false choices.

The configuration file is saved in the Data folder as Prefs.dat; here is its structure.

[Settings]
BackgroundGraphic=
HotKey=
HotKeyModifierMask=
LockAltEscape=
LockAltTab=
LockCtrlEscape=
LockShutdown=
LockTaskManager=
LockWindowsKey=
Mode=
PutKidSafeOnTop=
TimeOut=
UnlockText=
UsePasswordDialog=
UseSystemTrayIcon=

BackgroundGraphic - the path to the image used as the background graphic for the KidSafe window. Images in BMP, GIF and JPG/JPEG format are guaranteed to work; other image formats may work, but probably won't unless you have QuickTime installed on your computer. Because of this restriction, only BMP, GIF and JPG/JPEG images are shown in the Options dialog; if you want to use another image type, you'll need to manually edit the configuration file.
If you specify a file that doesn't exist or isn't an image file, KidSafe will use its default background graphic instead.

HotKey - a numerical value from 0 to 255. Specifies the virtual-key code for the KidSafe hotkey. (Unless you're a programmer, you probably don't want to edit this manually; it's easy to break something, and somewhat difficult to get the correct value)

HotKeyModifierMask - a numerical value. Specifies whether the hotkey should include the Ctrl key, the Alt key, the Shift key, the Windows key (also known as the Start key), or a combination of these.

LockAltEscape - true or false. Specifies whether the Alt-Escape key sequence should be disabled or not.

LockAltTab - true or false. Specifies whether the Alt-Tab key sequence should be disabled or not.

LockCtrlEscape - true or false. Specifies whether the Ctrl-Escape key sequence should be disabled or not.

LockShutdown - true or false. Specifies whether the system shutdown is disabled or not. (Note: even if LockShutdown is set to true, trying to shutdown the computer might close some of your applications. This is a limitation of Windows, not KidSafe)

LockTaskManager - true or false. Specifies whether the Task Manager should be locked or not. (Note that any running Task Manager instances will be closed)

LockWindowsKey - true or false. Specifies whether the Windows key (aka the Start key) should be disabled or not. If set to true, it will also disable all key combinations involving the Windows key, including Windows+R (run a program) and Windows+M (minimize all windows)

Mode - 0, 1 or 2. Specifies whether KidSafe should be in normal mode, screensaver mode or hotkey mode. If set to 0, KidSafe will immediately open its fullscreen window; if set to 1, KidSafe will run in the background and monitor the system. KidSafe will essentially behave like a screensaver, checking for system activity; if the system remains inactive for the number of seconds specified by TimeOut, KidSafe's fullscreen window will open. This could be extremely useful for someone who has to leave their computer periodically, since KidSafe won't activate until the computer's been idle for the time period specified by TimeOut's value. If Mode is set to 2, KidSafe will run in the background and wait for you to press the user-defined hotkey that activates KidSafe.

PutKidSafeOnTop - true or false. Specifies whether the KidSafe window should be placed on top of every window (including the Start Menu and Alt-Tab dialog) or not.

TimeOut - a number value. If Mode is set to 1, KidSafe will run in the background and monitor the system. KidSafe will essentially behave like a screensaver, checking for system activity; if the system remains inactive for the number of seconds specified by TimeOut, KidSafe's fullscreen window will open. This could be extremely useful for someone who has to leave their computer periodically, since KidSafe won't activate until the computer's been idle for the time period specified by TimeOut's value.

Unlocktext - the text you'll need to type in the unlock box to turn KidSafe off. Make sure you'll remember this, because it can't be recovered once you enter it. YOU CAN'T EDIT THIS IN THE Prefs.dat FILE; IT'S SPECIALLY ENCODED IN A NON-RECOVERABLE FORMAT.

UsePasswordDialog - true or false. If set to true, the unlock textbox will display a string of asterisks (*) instead of the actual unlock text when you type it. This can be extremely useful if you're trying to stop kids who are old enough to read - they won't be able to see what you're typing.

UseSystemTrayIcon - true or false. If set to true, KidSafe will show its icon in the system tray; double-clicking the tray icon will show the KidSafe window. (The tray icon is only shown in screensaver mode or hotkey mode, since it isn't necessary in normal mode.) The tray icon also serves as a reminder that KidSafe is running.

The default setting for each of these options is false (to be precise, the default setting is false, 0, or nothing, depending on the value type); if you want to lock anything, you'll need to manually set the value of its setting to true. This is a safety limitation designed to avoid accidentally locking something you didn't want locked.

The license of this software is Free, you can free download and free use this system locking software.