So, you have "never" under sleep? What about hibernate or "Turn off display"?
Right clcik the desktop - personalise.
Click (over bottom right) "screen saver"
What do you have there?
Select "None" if you have anything else. Reboot and see if the computer still goes to sleep.
Have you actually disabled the hibernate function? I'm wondering if the PC is actually hibernating, not sleeping. This link should show you how to disable hibernate. This should let you know whether it's a hibernate problem or not.