I am trying to use 3DMark11 and the system goes to the lock screen after 5 minutes which stops the app. Things I have tried:

-Set all power all to 'Never'
-Un-install 'Mail' app. I read somewhere this can cause this same issue.
-Download reg hack to add back in the console option to the power settings.
-Turn off the screensaver.
-Installed 'Move Mouse'. Does nothing that I can see.

I am using Win 8 Pro so there is no option to reset the security policies, as some have mentioned works. This problem doesn't occur when watching movies, etc.