Dell XPS 15 (L521X, Mid 2012) - Manual (Page 10)

After Working Inside Your Computer
After you complete replacement procedures, ensure the following:
• Replace all screws and ensure that no stray screws remain inside your computer.
• Connect any external devices, cables, cards, and any other part(s) you removed
before working on your computer.
• Connect your computer and all attached devices to their electrical outlets.
CAUTION: Before turning on your computer, replace all screws and ensure
that no stray screws remain inside the computer. Failure to do so may damage
your computer.
10 | After Working Inside Your Computer