Hardware Reference
In-Depth Information
copyright message, and displays the DOS prompt.
The Windows 9x/Me Boot Process
The Windows 9x/Me boot process involves two files: IO.SYS and WIN.COM. For more information,
see “The Windows 9x/Me Boot Process” in
Upgrading and Repairing PCs
, 19
th
Edition, included in
its entirety on the DVD packaged with this topic.
Windows 2000/XP Startup
When you start a Windows 2000 or XP system (which is based on the same set of integral code that
originated with Windows NT), the boot process is different from that of a DOS or Windows 9x/Me
system. Instead of accessing the IO.SYS and MSDOS.SYS files used by 9x/Me, these operating
systems use an OS loader program called
Ntldr
.
The basic startup process is described in the following step-by-step procedures:
1.
The partition boot sector loads Ntldr (NT Loader). It then switches the processor to protected
mode, starts the file system, and reads the contents of Boot.ini. The information in Boot.ini
determines the startup options and initial boot menu selections (dual-booting, for example). If
dual-booting is enabled and a non-NT/2000/XP OS is chosen, Bootsec.dos is loaded. If SCSI
drives are present, Ntbootdd.sys is loaded, which contains the SCSI boot drivers.
2.
Ntdetect.com gathers hardware configuration data and passes this information to Ntldr. If more
than one hardware profile exists, Windows uses the correct one for the current configuration. If
the ROM BIOS is ACPI compliant, Windows uses ACPI to enumerate and initialize devices.
3.
The kernel loads. Ntldr passes information collected by Ntdetect.com to Ntoskrnl.exe. Ntoskrnl
then loads the kernel, Hardware Abstraction Layer (Hal.dll), and Registry information. An
indicator near the bottom of the screen details progress.
4.
Drivers load and the user logs on. Networking-related components (for example, TCP/IP) load
simultaneously with other services, and the Begin Logon prompt appears onscreen. After a user
logs on successfully, Windows updates the Last Known Good Configuration information to
reflect the current configuration state.
5.
PnP detects and configures new devices. If new devices are detected, they are assigned
resources. Windows extracts the necessary driver files from Driver.cab. If the driver files are
not found, the user is prompted to provide them. Device detection occurs simultaneously with
the operating system logon process.
The following files are processed during startup:
• Ntldr
• Boot.ini
• Bootsect.dos (multiple-boot systems only)
• Ntbootdd.sys (loaded only for SCSI drives)
• Ntdetect.com
• Ntoskrnl.exe
• Hal.dll
• Files in systemroot\ System32\ Config (Registry)
