Introducing the Notebook Computer Identifying Parts of the Computer Bottom View 19. Modem port (on certain models). 20. LAN port (on certain models). 24. Main battery. 25. Plug-in module bay. Can contain a CD-ROM or DVD drive, floppy disk drive, secondary battery, or other plug-in module. 21. PC Card and CardBus slots (upper and lower). 22. Hard disk drive. 23. Main battery latch. 26. Mini-PCI cover (no user parts inside). 27. RAM cover. 14 Reference Guide