Windows NT/2000 Structure

Windows NT and 2000 are 32 bit operating systems that run in 2 different modes which are kernel(protected) and user. Applications use Application Program Interfaces(APIs) to pass threads between the 2 modes. User mode provides no direct access to the system's hardware. The subsystems of these operating systems are outlined below.

WIN32 -- This subsystem handles support for 32-bit windows applications and is also known as the Client/Server subsystem. This subsystem has the following features:

·       32-bit architecture

·       Multiple execution threads are supported for each process

·       Memory Protection - each Win32 application is separated and protected from other applications

·       OpenGL - Support for 2D and 3D graphics cards

·       2GB nonsegmented address spaces are assigned to each application

·       NT/2000 supports DOS applications via VDMs(Virtual DOS Machines). A VDM is a Win32 application that creates an environment where DOS applications can run. It does this by making the NT Workstation resemble a DOS environment and tricks the DOS applications into thinking that they have unrestricted access to the computer's hardware. NT can only support DOS applications that use VDDs(Virtual Device Drivers) to intercept the applications calls to the computer's hardware.

·       NT/2000 also supports Win16 applications with the use of a DOS application called WOW(Windows on Windows). WOW runs within a VDM that runs as a 32-bit process. If a Win16 application crashes it will only corrupt the WOW, but will not affect the rest of the NT operating system.

In addition to the above, Windows 2000 also adds the Plug and Play Manager and the Power Management Manager

The boot files used by NT/2000 are completely different than Windows 9x and are listed below:

• BOOT.INI - Specifies boot defaults, operating system locations, settings and menu selections.
• BOOTSECT.DOS - A file located in the system partition that allows the option to boot into another operating system such as Win98 or DOS.
• NTDETECT.COM - Hardware detection program that is located on the root of the system partition.
• NTLDR - File that loads the operating system and is located on the root of the system partition.
• NTOSKRNL.EXE - The executable file.
• OSLOADER.EXE - This is the OS loader for RISC based systems.
• NTBOOTDD.SYS - File used when the system or boot partition is located on a SCSI drive and the BIOS is disabled.

The registry editors included with Windows NT/2000 include Regedt32 and Regedit. For Windows 2000, the Regedt32 tool should be used while Windows NT can use either. Most of the registry(the static items) are contained in hive files which are located in the \WINNT\SYSTEM32\CONFIG directory. The 5 hives are SAM, security, software, system and default.

In Windows 2000 most system administration tasks are performed in the Computer Management Console that contains all of the various Microsoft Management Consoles(MMCs) in one location. Windows 2000 filenames can be up to 215 characters long and cannot contain the following: <>\/?*"|  and Windows 2000 supports PnP while NT does not.

File Systems
The following are common hard disk configurations.

• Partition - A partition is a portion of a physical hard disk. A partition can be primary or extended
• Primary Partition - This is a bootable partition. One primary partition can be made active.
• Extended Partition - An extended partition is made from the free space on a hard disk and can be broken down into smaller logical drives. There can only be one of these per hard disk.
• Logical Drive - These are a primary partition or portions of an extended partition that are assigned a drive letter.
• Volume - This is a disk or part of a disk that is combined with space from the same or another disk to create one larger volume. This volume can be formatted and assigned a drive letter like a logical drive, but can span more than one hard disk. A volume set can be extended without starting over, however to make it smaller, the set must be deleted and re-created.

There are various management tools that can be used to configure drives. The Disk Management MMC is a snap-in for the Computer Management Console in Windows 2000. You can create partitions, volume sets, logical drives, format disks, etc. NT 4.0 had a similar tool called the "Disk Administrator". DOS and Windows 9x utilize the FDISK utility.

When discussing Windows file systems you need to understand what File Allocation Tables(FAT) are. FAT is a table that an operating system maintains in order to map the clusters(the smallest unit of storage) that a file has been stored in. When files are written to a hard disk, the files are stored in one or more clusters that may be spread out all over the hard disk. The table allows Windows to find the "pieces" of your file and reassemble them when you wish to open it.

There are several different types of file systems that are explained below:

• FAT16 - FAT16 table entries are 16 bits in length limiting hard disk sizes to 2GB. Note that even if the OS supports larger partition sizes, the BIOS must also support logical block addressing(LBA) or the maximum partition that you will be able to create will be either 504 or 528 MB.
• FAT32 - Created to allow more efficient use of hard drive space and allowed for partitions up to 8GB using 4KB cluster sizes. In order to format a drive as FAT32, the "Large disk Support" must be enabled when starting FDISK. FAT32 is not compatible with older versions of Windows including Windows 95A and NT. In Windows 9.x, the CVT1.EXE can be used to convert FAT16 partitions to FAT32.
• NTFS4 - NTFS4 is the file system used by Windows NT that provides increased security and reliability over other file systems. On an NTFS partition, you can't boot from a DOS boot disk - this is one of the security features of NTFS. Additionally, a floppy disk cannot be formatted as NTFS. For this reason it might not be a bad idea to have a small partition formatted FAT so that you can boot into DOS for recovery purposes. In order to convert a FAT partition to NTFS, NT includes a utility called convert.exe.
• NTFS5 - This is the native file system for Windows 2000. NTFS5 has many new features as follows:
• Encrypted File System(EFS) - Windows 2000 NTFS volumes have the ability to encrypt data on the disk itself. Cipher.exe is a command line utility that allows for bulk or scripted file encryption.
• Disk Quotas - Provides the ability to set space limitations on users on a per volume basis.
• Defragmentation - Windows 2000 now includes a disk defragmenter that can be used on NTFS partitions.
• Volume Mount Points - Provides the ability to add new volumes to the file system without having to assign a drive letter to them. This feature is only available on an NTFS partition using dynamic volumes.
• Compression - In Windows 2000 files, folders and entire drives can be compressed by right clicking on the item to be compressed and selecting "properties" and then "advanced".

The convert.exe utility can be used to convert a FAT or FAT32 partition to NTFS.

• HPFS - Stands for High Performance File System and is used with OS/2 operating systems. This file system can only be accessed by Windows NT 3.51 and OS/2.

Windows 9x operating systems also employ VFAT which is a protected-mode FAT file system that prevents DOS and the BIOS from accessing resources. VFAT is the replacement for SMARTDRV.SYS and uses a driver called VCACHE.

Operating System	Supported File Systems
DOS	FAT16
Windows 3.x	FAT16
Windows 95A	FAT16
Windows 95 OSR2	FAT16, FAT32
Windows 98	FAT16, FAT32
Windows 98SE	FAT16, FAT32
Windows NT 4	FAT16, NTFS
Windows 2000	FAT16, FAT32, NTFS

In addition to the disk administration utilities previously mentioned, information about a drive can be displayed by right clicking the drive in My Computer or Windows Explorer & select Properties

Here you can view the amount of used and freespace on the drive, the capacity and the file system. The tools tab provides access to defragmentation, scandisk and backup utilities in Windows 98. Windows NT/2000 contain these items as well as a few additional. The 3rd tab is for sharing the drive and setting permissions on it so that it can be accessed across the network.

Backing up drives allows you to recover your data or even the entire system if a catastrophe occurs. There are several different types of backup:

• Full - copies all files and marks them as being backed up.
• Incremental - copies only files created/changed since last full backup and marks them as being backed up.
• Differential - copies only files created/changed since last full backup and doesn’t mark them as being backed up.
• Daily - copies only files created/changed today and doesn’t mark them as being backed up.

In DOS backups can be run with the BACKUP command. There are several switches that can be added to the command.

• /S - Forces all files and subdirectories to be backed up.
• /M - Only modified files are backed up.
• /D - Backs up files modified after a specific date.
• /T - Backs up files modified after a specific time.

The Windows 98 backup utility can be accessed via Start>Programs>Accessories>System Tools>Backup and also via right clicking on a drive in My Computer and selecting the tools tab as previously mentioned.

There are several different hard drive utilities that can be found in the various versions of Windows that are listed below:

• CHKDSK - This utility is run from a DOS prompt and recovers lost allocation units on a drive that can occur when an application or the system are ended unexpectedly. The /F switch converts the lost units into a format such that the units can be viewed and deleted. Can be found in all versions of windows.
• SCANDISK - The ScanDisk utility inspects the hard drive for errors and corrects them. Scandisk is available in DOS 6.x and Windows 9x.
• DEFRAG - Reorganizes data on the disk for optimal disk performance. In DOS this utility was run from a DOS prompt. In Windows 9x and 2000 this utility can still be run from a prompt or can be accessed at Start>Programs>Accessories>System Tools>Disk Defragementer. Windows NT did not come with a defragmentation utility.
• DRIVESPACE - This utility for windows 9x offers many of the same features as NT's disk administrator including compression, formatting and drive information.

Installations and Upgrades
All new Windows installations start with using FDISK(or 3rd party utility) to partition the drive followed by a reboot and then the formatting of the drive.

Windows 98 New Installation
In order to install Windows 9x the following minimum hardware requirements must be met. The system must be at lease a 486DX, 66MHz processor or higher, 16 MB RAM, VGA Video adapter and display, 225 MB free FAT16 hard disk space or 175 MB free FAT32 hard disk space.

Unlike Windows 95, Windows 98 does not have to be installed over another operating system such as DOS and does not require access to a FAT16 partition.

The typical method for installing Windows 98 is to boot the computer from the installation CDROM. This requires that the system's CDROM drive is bootable and that the BIOS is configured for this. First Scandisk will be run and if no errors are found, the GUI portion of the setup process will begin which includes the following stages:

1.  Preparing to Run Windows 98 Setup

2.  Collecting Information About Your Computer

3.  Copying Windows 98 Files to Your Computer

4.  Restarting Your Computer

5.  Setting Up Hardware and finalizing Settings

6.  Restart

Upgrade from Windows 3.x to Windows 95
This upgrade is performed by running Setup.exe located on the installation CDROM. When you upgrade from Windows 3.x to Windows 95, you'll find that settings in protocol.ini, system.ini, and win.ini are used to create the Windows 95 Registry. These files and any files with the .GRP extension are saved for backward compatibility.

Upgrade from Windows 95 to Windows 98
This is typically the easiest upgrade and involves loading the Windows 98 CDROM and executing setup.exe. This will lauch the setup program that will go through the same stages as for a clean install, however, any usable information that is available from Windows 95 will be used during the upgrade. Note that CMOS antivirus software can cause an upgrade to fail during the 1st stage of the installation process. Information about failures can be found in the SETUPLOG.TXT file. If Windows 98 is installed to a directory other than the Windows directory, all previously installed applications will have to be reinstalled.