Dell Precision 330 - Manual (Page 59)

Installing Upgrades 59
c Rotate the cover downward and into position. Ensure that the two
cover release buttons click into place.
Re p l a c i n g t h e C o v e r ( D e s k t o p C h a s s i s )
Interior Service Label
A service label affixed to the inside of your computer cover indicates the
location of system board components and connectors.
cover release buttons (2)
hooks (3)
recessed
slots (3)