Prevent iMac from sleeping, for VPN login? We have an iMac in the office, and I have been getting inconsistent access when trying to log in to it. The firewall isn't going down, since I can connect to the VPN. After discussing it with the people at the office, we suspect that the iMac is going to sleep. 

Is it possible to keep the iMac "awake" 24 hours a day? How do I instruct the people at the office to configure the iMac? What settings should be changed? The iMac is running OS X Lion 10.7.3.
You can disable sleeping in the Energy Saver preference pane of System Preferences.





Alternatively, you can use a free app called Caffeine to easily prevent your Mac from sleeping just with a click of the mouse.  Both work exactly the same, but Caffeine makes it easier to dynamically switch between the two settings.