On a Dell Latitude 5450 laptop, the setting to prevent the computer from going to sleep when the lid is closed does not work during the first system startup. I have an external monitor connected as an extended display—not cloned—along with a keyboard and mouse. During startup, the external monitor displays a screen prompting me to enter the password for hard drive encryption. After entering it, the system boots up and then goes into sleep mode. I have to open the laptop lid, wake the computer from sleep, log in, and then I can close the lid—at that point, the setting to prevent the PC from going to sleep works.