KeyFreeze is a tiny tool which locks your PC, so that touching the keyboard and mouse won't have any effect (perfect if you're leaving the system unattended and have children playing nearby).
You could always lock your system by pressing Win+L, of course, but that hides the current contents of the screen. KeyFreeze will leave everything visible, just as it was, which means you can have a movie playing, carry out a web chat, perhaps monitor the progress of some lengthy task you're running - whatever you like.
The program is extremely straightforward. When you need to lock your system, just launch it. You'll see a five second countdown, just long enough to rearrange any application windows to suit your needs. Your mouse and keyboard will then effectively be disabled, with a single exception: pressing Ctrl+Alt+Del unlocks your system and you'll be able to carry on as normal.
The Ctrl+Alt+Del hotkey is fairly easy to guess, of course, so you shouldn't think of KeyFreeze as a security tool. It's not about protecting your system from attack, rather just reducing the chance of small children, perhaps wandering pets from knocking the mouse or keyboard and causing problems. The program carries out this more basic task very well, though, and if you could benefit from making your PC a little more tamper-proof then we'd give it a try.