The A+ Certification & PC Repair Handbook (Charles River Media Networking/Security)

The overall system starting order for a typical system is covered in Chapter 23. As you may recall, the exam may look for POST, BIOS, boot sector, and GUI as the overall system starting order. To reveal what happens behind the scenes when a computer system is turned on and booted into Windows 9x, we will break down the start order into the POST/BIOS, Real Mode load, Protected Mode load, and GUI load.

POST/BIOS

When the system is first powered up, the POST is loaded by the ROM BIOS. Next, the MBR is read by the Bootstrap loader, which determines the operating system that is loaded into the system’s memory.

Real Mode Load

After the system BIOS has run and the OS is loaded into memory, 16-bit Real Mode drivers are loaded. This is how Windows 9x maintains backward compatibility with DOS and Windows 3x. In this sequence of the start-up process, IO.SYS, MSDOS.SYS, CONFIG.SYS, COMMAND.COM, and AUTOEXEC.BAT are processed.

Note

As mentioned in Chapter 23, Windows 9x uses its 32-bit drivers in place of the AUTOEXEC.BAT and CONFIG.SYS files. These files are not needed by Windows 9x; they are there simply to maintain backward compatibility.

Protected Mode Load

In this phase of the Windows 9x start-up process, WIN.COM is used to start up Windows 9x. Next, VMM32.VXD, which contains an entire package of Windows 9x 32-bit virtual device drivers, loads necessary drivers (VxDs) into memory.

Note

The VMM that was used to load 16-bit and 32-bit device drivers for Windows 3.x is replaced in Windows 9x with VMM32.VXD.

Finally, the SYSTEM.INI file is processed for any device drivers it may contain that need to be loaded.

GUI Load

In the final phase of the Windows 9x start-up process, the KERNEL32.DLL, KRNL386.EXE, GDI.EXE, GDI32.EXE, USER.EXE, and USER32.EXE are loaded, and the user is finally presented with the Windows interface screen known as Explorer.

Start-up Menu And Options

If the operating system cannot boot into Windows 9x successfully, the Windows 9x Startup Menu will most likely appear. The Startup Menu interacts with MSDOS.SYS (which should have a minimum size of 1024K for a stable OS environment) and is used to isolate and troubleshoot problems related to system start-up. You can access the Startup Menu manually by pressing the F8 function key just before the Windows 9x splash screen appears on your display. The Startup Menu offers eight configuration options for various diagnostic and configuration purposes. The Startup Menu and its eight options are explained next:

  1. Normal: This option is used to simply boot the system up normally. No special drivers are added or removed with this configuration.

  2. Logged (BOOTLOG.TXT): This option is similar to the Normal option. The only exception is that the steps of the start-up process are written to the file BOOTLOG.TXT.

  3. Safe Mode (Press F5): This is considered the most useful mode for troubleshooting purposes. Safe Mode loads a generic VGA driver for basic video, a keyboard driver, and HIMEM.SYS (which manages extended memory). Safe Mode does not load the configuration files AUTOEXEC.BAT and CONFIG.SYS. It does not load NIC, modem, and other specialized drivers. Safe Mode is an excellent tool for troubleshooting drivers that do not work properly with the operating system. For example, if, after installing a new advanced video driver, you can no longer view the screen, simply reboot the computer and enter Safe Mode. Safe Mode loads a basic set of drivers that allow you to remove the new video driver from the system and reboot normally.

    Note

    You can also enter Safe Mode directly by pressing the F5 function key before the Windows 9x splash screen is displayed.

  4. Safe Mode with Network Support (Press F6): This option also allows you to enter Safe Mode and loads support for networking devices and connections. By pressing the F6 function key before the Windows 9x splash screen is displayed, you can directly enter Safe Mode with network support.

  5. Step-by-step configuration (Press Shift+F8): When this option is used, you are prompted as to which configuration files and file lines will be executed on start-up. For example, if you press the Shift+F8 keys before the Windows 9x splash screen is displayed, you will be asked if you would like to process such files as the CONFIG.SYS and AUTOEXE.BAT. If you enter “Y” for yes, you will be asked if you would like to process each line of each of these files. This is an excellent way to troubleshoot individual devices and settings that are loaded by each file, one line at a time.

  6. Command prompt only (Press Shift+F5): This option is used to start up the system in MS-DOS. It is often used for troubleshooting purposes if Safe Mode doesn’t work.

  7. Safe Mode command prompt only: This option is used to start DOS without network support. The major configuration files are bypassed, and you are directed to a command prompt.

  8. Previous version of DOS (Press F4): This option is available if a previous version of DOS is installed on your system. Pressing the F4 function key before the Windows splash screen appears will get you there.

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