MRT Lock

MRT Lock is a straightforward piece of software that gives you the possibility to schedule the computer to automatically lock on countdown and at Windows startup.
It has a handful of options that can be easily configured, even by users with little or no previous experience in OS tweaking tools.

Simple setup and interface

It's easy to install and set up, since it has familiar wizard steps and doesn't require any libraries or other software components to run.
As far as the interface is concerned, MRT Lock has a small window that reveals all options put at your disposal.

Easily lock the computer

You can instruct the utility to run at every Windows launch until told otherwise, automatically lock the machine at startup, lock it on the spot or on countdown (in seconds), and set a hotkey combination to accomplish this task.
All changes are applicable with one click and the program can be minimized to the taskbar to become non-intrusive and let you carry on with your normal PC activity until the lockdown timer is up.

Evaluation and observations

We have experienced some issues on newer Windows editions. After lockdown, the application didn't respond to commands when we attempted to unlock it by triggering the default hotkey combination.
This issue was finally resolved after managing to close MRT Lock, which was a particularly difficult task, since it quickly made any selected window inactive and restricted us from accessing the Task Manager. It didn't cause any more trouble after changing the default keyboard shortcut, however.

Conclusion

All in all, MRT Lock has simple and clear-cut options for PC lockdown, but you should make sure to set a custom hotkey combination before securing the PC. We must also keep in mind that it hasn't received updates for a long time.