I am looking for a way to disable a Windows PC for x minutes every y minutes, ( 15 minutes every 1 hour for example ), where the pc is disabled/frozen, or the keyboard/mouse frozen for an interval and at the end of the interval becomes operable again, and to repeat this regiment in a loop throughout the time the software is activate - 45 mins on (for example) followed by 15 minute freeze (for example).
What can be done?
Using Autohotkey, write a small script that opens device manager and disables the keyboard and mouse under 'human interface devices' - You will also need to write a script to switch them back on. Place disable script on a schedule for every 45 mins, then the enable script after that for whatever time you need it disabled.
if user is guest user you could allow specific time to login into the account,else two options come to mind
1) set a screensaver for specific time with some specific date and time
else
2) setting with some preferences for power scheme
According to this website
The first is to configure a screen saver with the required timeout and a password requirement. This can be done under User Configuration\Policies\Administrative Templates\Control Panel\Personalization. The required settings are: 'Enable screen saver', 'Screen saver timeout', 'Force specific screen saver' (this is important because if the system has no screensaver configured this won't work) and finally 'Password protect the screensaver'. The setting names and paths here are based on using the GP management console on Windows 7 or Windows Server 2008/R2 since best practice is to edit GPOs using the most current OS in your environment. If using an older version of the console, the same settings are available in a different location (I think its under the display control panel but I don't have an XP or 2003 system to verify).
The second option is to use a group policy preferences power plan (or Power Scheme and options if using Windows XP) as Alan indicated. The plan should be configured to cause the computer to sleep after 15 minutes (just turning off the display wouldn't lock the computer) and set to require a password upon waking. This option is a little more involved since it not only configures the computer to enter sleep mode (which can cause delays and problems when waking) but also support for group policy preferences (available with Windows XP SP3, Vista SP1 and Windows 7).
Hope it helps
