Steps
Windows XP
1.Go to Start then Control Panel and click on Power Options
2.On the Power Schemes tab, select Home/Office Desk in the Power Schemes drop-down box
3.In the box labeled System standby, select Never
4.Click OK to save your changes.
Windows Vista
1.Go to start and type in the search box Power Options hit the enter button
2.On the Left side there is a panel Click Change when the computer sleeps
3.Click the drop-down box which says Put the computer to sleep and select Never
4.Click Save changes
Mac OS X
1.Click on the blue apple icon in the upper left corner of your screen, and choose System Preferences
2.In the Hardware section, select Energy Saver
3.Make sure the Settings for: drop-down box is set to Power Adapter
4.On the Sleep tab, move the sliding bar labeled Put the computer to sleep when it is inactive for: to Never
1.Laptop users may want to enable sleep mode when running on battery power.
2.When Sleep mode is disabled you screensaver will still come up.