I'll outline my situation first of all:
I work at a university, and we have a problem where students tend to lock their PCs and, being the free-minded youths that they are, just walk away and leave them locked, thus requiring an admin to go and unlock it. This is especially a problem at exam time as we frequently run out of available PCs.
So the solution is thus - devise a method for logging the student out if the PC is left locked for more than 15 minutes. This was simple enough, using a service to catch the OnSessionChange event and setting up a timer to do the rest.
The problem now is how to notify the user about this. Ideally, a Yes/No box when they go to lock the PC, either via Win+L or Ctrl-Alt-Del->Lock Computer, would be great, but I'm not sure if that is possible. I experimented with creating an application and using Global Keyboard Hooks, but this was fairly useless when going through C-A-D and I had trouble getting it to recognise both the Windows key and L simultaneously.
Failing that, the option to display a warning message after the PC has been locked would suffice. I have been able to make a message box appear with no problems, but "the powers that be" want a proper full screen warning about what will happen if the PC is left locked. I have tried creating a form to appear, but it doesn't seem to want to play when the PC is locked. I've even tried getting the service to run an external application that would display the message, but to no avail.
So...yeah. What I am asking is:
1. Is what I want actually possible? Or is a little message box the best I'm going to get?
2. Is there a way to get an image to display on screen when the PC is locked?
Many thanks in advance for your help - I can provide some code that I have already tried if need be. :)