The sleep mode in Windows Vista/7 that closelyresembles the "Standby" option In Windows XP allows a user to conserve the energy when the computer is not used. The default Windows settings are to automatically activate this option after the certain period of the computer inactivity- typically 15 to 30 minutes. In the sleep mode data are stored in the computer memory (RAM) rather than on the hard drive. As a result all unsaved data would be lost if your computer won't wake up for some reason. Use Windows Control panel to turn off the sleep option on your machine.
In Windows Vista or 7
Click "Start" in Windows to open the start menu.
Click "Control Panel" and then choose the "Hardware and Sound." Then click "Power Option."
Click on the task "Change when the computer sleeps"
Click on the drop-down box "Put the computer to sleep" and choose the option "Never."
Click the button "Save changes" to turn off the sleep mode.
In Windows XP
Click "Start" in Windows and then choose "Control Panel".
Click "Performance and Maintenance" and select "Power Options."
Click on the tab "Power Schemes" in the "Power Options" window.
Click on the drop-down box "System standby" and choose the option "Never." Then click "OK."