CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [239]
You know from earlier chapters that to make a drive bootable requires an active, primary partition, right? Let’s look at the process in a PC with a hard drive partitioned as C: and D:.
The CPU wakes up and runs the system BIOS, and then the BIOS sends out a routine looking for a valid operating system in the boot sector of the primary master hard drive. The master file table (MFT) lives in the boot sector of the C: partition. It points to the location of the Windows 2000/XP system files, also on the C: drive, because that’s the bootable drive. Windows calls the primary active partition the system partition or the system volume (if it’s a dynamic disk).
The Windows 2000/XP boot files consist of NTOSKRNL.EXE (the Windows kernel), the \WINNT\SYSTEM32\CONFIG\SYSTEM file (which controls the loading of device drivers), and the device drivers. Although these files are the core of the Windows 2000/XP OS, they are not capable of booting, or starting, the system. For that feat, they require NTLDR, NTDETECT.COM, and BOOT.INI—the system files.
The system files start the PC and then, at the end of that process, point the CPU to the location of the boot files. The CPU goes over and chats with NTOSKRNL, and the GUI starts to load. The operating system is then up and running, and you’re able to do work.
The odd part about all this is that Microsoft decided to make the OS files mobile. The Windows operating system files can reside on any partition or volume in the PC. The \ WINDOWS folder, for example, could very well be on drive D:, not drive C:. Whichever drive holds the core OS files is called the boot partition. This can lead to a little confusion when you say the system files are on the C: drive and Windows is on the D: drive, but that’s just the way it is. The vast majority of Windows 2000/XP systems have the system partition and the boot partition both on the same big C: partition.
You have the process now in general, so let’s look more specifically at the makeup and function of the individual files involved in the boot process.
2000/XP System Partition Files
Windows 2000 and XP require the three system files in the root directory of the system partition:
NTLDR
BOOT.INI
NTDETECT.COM
To see these files, go into My Computer and open the C: drive. Go to Tools | Folder Options. Click Show hidden files and folders, uncheck the Hide protected operating system files (Recommended) option, and click OK. Now when you return to viewing the folder in My Computer, you will see certain critical files that Windows otherwise hides from you to prevent you from accidentally moving, deleting, or changing them in some unintended way (Figure 14-49).
NTLDR
When the system boots up, the master boot record (MBR) or MFT on the hard drive starts the NTLDR program. The NTLDR program then launches Windows 2000/XP or another OS. To find the available OSs, the NTLDR program must read the BOOT.INI configuration file. To do so, it loads its own minimal file system, which enables it to read the BOOT.INI file off of the system partition.
BOOT.INI File
The BOOT.INI file is a text file that lists the OSs available to NTLDR and tells NTLDR where to find the boot partition (where the OS is stored) for each of them. The BOOT. INI file has sections defined by headings enclosed in brackets. A basic BOOT.INI in Windows XP looks like this:
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition\WINDOWS="Microsoft Windows XP
Professional" /fastdetect
Figure 14-49 My Computer showing the system files
A more complex BOOT.INI may look like this:
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition\WINDOWS="Microsoft