Dell OptiPlex 330 User Manual page 211

CAUTION:
To avoid electrical shock, laceration by moving fan blades, or other
unexpected injuries, always unplug your computer from the electrical outlet
before removing the computer cover.
NOTICE:
Be careful when opening the computer cover to ensure that you do not
accidentally disconnect cables from the system board.
1
6
1 drives bay (CD/DVD, floppy, and hard
drive)
3 system board
5 heat sink assembly
2
2
4
6
5
power supply
card slots
front I/O panel
Desktop Computer Parts
3
4
211