Comparing Windows 9xMe with Windows NT2000XP

Comparing Windows 9x/Me with Windows NT/2000/XP

Windows NT 4.0, Windows 2000, and Windows XP are three successive versions of what you could call "Windows for business." These versions of Windows, unlike Windows 9x/Me, have no leftover MS-DOS or Windows 3.1 components , and until the development of Windows XP, weren't all that concerned about working with MS-DOS, Windows 3.1, or Windows 9x/Me applications. Instead, these versions of Windows put stability and speed above everything from the moment you push your computer's power switch.

From configuration files to the Windows kernel itself, Windows NT 4.0, Windows 2000, and Windows XP are very different from their predecessors (and sometimes from each other).

Windows NT 4.0/2000/XP Boot Sequence

The following files are required to start these versions of Windows:

• NTLDR ” The Windows NT 4.0/2000/XP loader program.

• Boot.ini ” Options in this file affect how Windows starts up.

• Bootsec.dos ” This contains the boot sectors for another operating system if you are multibooting .

• Ntdetect.com ” This detects the hardware installed on your system.

• Ntbootdd.sys ” This device driver is used only if Windows is being started from a SCSI drive whose host adapter does not have an onboard SCSI BIOS enabled.

• Ntoskrnl.exe ” The Windows kernel, which completes the boot process after being initialized by NTLDR .

• Hal.dll ” The Hardware Abstraction Layer, a software translator between Windows and system hardware.

• SYSTEM key in the Registry ” This is read to determine the system configuration.

• Device drivers ” These are loaded according to the information stored in the Registry.

NTLDR and Starting Windows NT 4.0/2000/XP

After the computer completes the POST and the system BIOS's bootstrap loader locates the NTLDR file, NTLDR

• Enables the user to select an operating system to start (if more than one is installed). NTLDR examines the contents of Boot.ini to find out which operating systems are installed.

• Loads the Windows startup files.

• Uses the Ntdetect.com program to determine what hardware is installed and places a list of the detected hardware into the Windows Registry.

• Loads Ntoskrnl.exe (the Windows kernel) and the Hardware Abstraction Layer ( Hal.dll ) into memory and hands over control to Ntoskrnl.exe after loading device drivers appropriate for the system configuration.

The NTLDR and Boot.ini files are located in the root directory (folder) of the default Windows drive if there is only one operating system. If you have a multiboot operating system (another version of Windows and Windows NT 4.0/2000/XP), the NTLDR and Boot.ini files (and Bootsec.dos , if required) are located in the root folder of the original operating system's default drive. For example, if you have Windows 9x installed on the C: drive and Windows XP installed on E:, these files will be in the root folder of the C: drive.

Windows NT/2000/XP Configuration Files

These versions of Windows have two major configuration files:

• boot.ini

• The Windows Registry

The following sections discuss these files in more detail.

Windows NT 4.0/2000/XP Boot.ini

The Boot.ini file is a specially formatted text file that configures the startup process for Windows NT 4.0/2000/XP. It resides in the default boot drive, even if Windows is installed on another drive.

On a multiboot system, Boot.ini indicates where the different versions of Windows are located. Here's the Boot.ini from my system:

 [boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /fastdetect C:\="Microsoft Windows" 

The [boot loader] section is configured to start the Windows version (Windows XP) installed on the second partition of the hard disk by default. It also provides a maximum time of 30 seconds to pause the dual-boot menu to enable the user to choose which version of Windows to run.

The [operating systems] section identifies the locations of the Windows versions on the computer. The first line states that Windows XP Professional is located in partition 2 of the first hard disk (disk 0). The second line indicates that the boot files for the previous version of Windows (Windows 98, in this case) are located in the root folder of the C: drive.

Windows XP also provides a command-line tool called Bootcfg , which can be used to insert the proper syntax for common commands. Bootcfg can also be used in the Windows XP Recovery Console.

Many additional options can be added to Boot.ini if necessary for troubleshooting. Boot.ini can be viewed with Notepad. However, if you need to configure Boot.ini to run your system in a troubleshooting mode, you should use MSConfig to view Boot.ini and configure it.

Windows NT 4.0/2000/XP Registry

As with Windows 9x/Me, Windows NT 4.0/2000/XP features a Registry, but you shouldn't be surprised to discover that the NT/2000/XP Registry is stored in different files, uses a different Registry editor, and has a different structure than its Windows 9x/Me sibling.

The Windows NT 4.0/2000/XP Registry is stored in different files (known in Windows-speak as hives ), roughly corresponding to different sections of the Registry. The following files are stored in the SYSTEM32\CONFIG folder beneath the default Windows folder (typically \Windows or \WinNT ); the backup file for each is listed in parentheses:

• default ( default.LOG ) ” Stores .DEFAULT settings from the HKEY_USERS section of the Registry.

• SAM ( SAM.LOG ) ” Stores part of the Security Account Manager database from the HKEY_LOCAL_MACHINE\SAM section of the Registry.

• SECURITY ( SECURITY.LOG ) ” Stores part of the Security Account Manager database from the HKEY_LOCAL_MACHINE\SECURITY section of the Registry.

• software ( SOFTWARE.LOG ) ” Stores software settings from the HKEY_LOCAL_MACHINE\SOFTWARE section of the Registry.

• system ( system.LOG ) ” Stores settings from the HKEY_LOCAL_MACHINE\SYSTEM section of the Registry.

caution

Boot.ini should not be modified unless you cannot start your computer. You should consult the Microsoft Knowledge Base for help in such cases. Fiddling with Boot.ini is not a good idea on a working system because unnecessary changes could stop your system from booting.

Windows XP also has two additional Registry hives for each user:

• ntuser.dat ( NTUSER.DAT.LOG ) ” Stores most user-preference settings in the \Documents and Settings\ username folder for each user.

• UsrClass.dat ( UsrClass.dat.LOG ) ” Stores user-preference settings for file associations and applications in the \Documents and Settings\ username \Local Settings\Application Data\Microsoft\Windows folder for each user.

caution

SAM and SECURITY sections of the Registry don't contain user-editable keys, so they appear to be empty. Don't be fooled ”and don't erase the matching Registry files either!

Windows NT 4.0 and Windows 2000 feature two Registry editors: Regedit and Regedt32 .

Regedt32 is the primary Registry editor for these versions of Windows; however, Regedt32 does not enable you to search for particular Registry values or data, but only for Registry keys. If you need to search for Registry values or data, use Regedit instead, which has the same look and feel as the Windows 9x/Me version of Regedit.

Windows XP uses Regedit as its sole Registry editor; if you use the Regedt32 command, this command also starts Regedit. Windows XP's Regedit, like the Regedit command in Windows NT 4.0 and Windows 2000, looks like the Windows 9x/Me version.

The Windows NT 4.0 and Windows 2000 Regedt32 Registry editor uses five separate editing windows, which can be resized and repositioned for viewing the Registry, as in Figure 18.4.

Figure 18.4. Regedt32 (Windows 2000 version; Windows NT 4.0 version is similar). Note the use of overlapping Windows for each of the Registry's major sections and additional menu options compared to Regedit.

Regedt32 also enables you to view the Registry in read-only form, making it the preferred Windows NT 4.0/2000 Registry tool for viewing the Registry's contents.

As with the Windows 9x/Me Registry, the Registry in Windows NT 4.0/2000/XP should not be edited by hand unless there is no alternative to solving a particular problem and unless the Registry has been backed up first.

You can use the Export option from the File menu of either Registry editor to make a backup copy with Windows NT 4.0 as well as with newer versions. However, Windows 2000 and Windows XP incorporate special features into their backup programs to make backing up the Registry easier.

To back up the Windows 2000 Registry, use the Windows 2000 backup program. Click Start, Accessories, System Tools, Backup to start it. From the opening menu, select Emergency Repair Disk, and select the option to back up the Registry on the next screen; insert a blank, formatted disk when prompted to complete the process.

Because the Windows 2000 Registry can occupy as much as 20MB of disk space on some systems, the Emergency Repair Disk (ERD ) does not contain a copy of the Registry itself but includes other information necessary to help restore the system in case of a crash. The Registry is stored in a folder called RegBack , which is contained in the \WinNT\Repair folder. In the event of a serious system problem, both the Windows 2000 Emergency Repair Disk and the Registry backup in the RegBack folder would be used to restore the system. You should re-create the ERD and Registry backup whenever you install new hardware or software to keep a record of the latest system configuration.

Windows XP also uses the Windows Backup program to back up the Registry as part of backing up the System State (see Figure 18.5). In Windows XP Professional, the System State also includes boot files, COM+ Class Registration database, and files protected by Windows File Protection. This backup is stored on tape or removable media.

Figure 18.5. Preparing to back up the Windows XP Registry as part of the System State backup using the Windows XP backup program.