Dell OptiPlex 745c (Early 2007) - Manual (Page 110)

Inside Your Computer
System Board Components
CAUTION: Before you begin any of the procedures in this section, follow the safety instructions located in the Product Information Guide.
CAUTION: To avoid electrical shock, 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 optical drive 2 floppy drive 3 power supply
4 optional chassis-intrusion switch 5 system board 6 heat-sink assembly
7 hard drive
1 fan connector (FAN) 12 internal USB (INTERNAL_USB)
2 processor connector (CPU) 13 battery socket (BATT)
3 processor power connector (12VPOWER) 14 PCI Express x16 connector