WinLock is a powerful security tool that allows you to take strict control over what other users can do on your PC.
If your kids are always messing around with your system settings, for instance, then in a few clicks you can prevent them from accessing the Registry editor, Control Panel, Display Properties, or even My Computer. Only someone who knows the central password (that'll be you, hopefully) will be able to bypass the protection and use the blocked settings.
You can also customise Explorer, perhaps hiding the Folder Options menu, or disabling the right-click context menu. You're able to set up User Account Control to suit your needs (and be sure that it'll stay that way). While the Drives pane allows you to prevent specified drives from being displayed in Computer or Explorer, and can block access to removable drives altogether.
WinLock is also able to prevent access to particular files, folders, or applications.
You can prevent users from viewing particular web sites. (This only works in Internet Explorer, but if you lock down other apps then that may be enough.)
If you're feeling really strict, then you can even limit the length of time that your PC can be running, so for example after a couple of hours it'll automatically close down.
Or, if you prefer a more hands-off approach, then you can have WinLock record the changes that your users make in its log file, for review later.