A Comparison between Windows 2003 and Windows 2000
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2003's Advantages over 2000
1) Domains can be renamed or moved to a differnt level in an AD tree.
2) Schema attributes can be deleted as well as added.
3) Any Domain Controller can cache the Global Catalogue thus preventing user logon problems if no Global Catalogue server is available.
4) AD Replication can be set not to use compression.
5) Cross-Forest Transitive Trusts can be created.
6) Many administrative tools allow drag-and-drop and there are more configuration and management wizards.
7) Most services are disabled by default in 2003 instead of enabled as in Windows 2000.
8) 2003 allows partial synchronisations of the Global Catalogue 2000 had always to have full synchronisations.
9) Support for IPv6. Ping and Tracert have extra IPv6 options.
10) Supports XML web services.
11) A new service called Volume Shadow Copy takes periodic snapshots of a hard drive making it easier to take backups and recover deleted files. Users can even be allowed to recover previous versions of files by themselves by using the Previous Versions client.
12) A Global Catalogue server can be built from backup media instead of by replication.
13) IPSec Nat Traversal - NAT-T - allows IPSec VPN clients and servers to pass through NAT firewalls. This is likely to lead to the wider adoption of L2TP VPNs.
14) Distributed File System DFS has had significant improvements made to it. For example DFS replicas can now be prestaged to avoid excessive initial file replication.
15) Multiple DFS Roots per server can be created (Enterprise and Datacenter editions only).
16) Print queue redundancy can be achieved by storing them on multiple servers.
17) Active Directory Migration Tool v.2.0 can now migrate users, computers, groups and passwords from an NT domain and can also perform the cross-forest migration of objects.
18) Terminal Server allows clients to map their local drives and printers
19) A terminal server client can connect to the console session where a greater range of administrative tasks can be performed.
20) Terminal Server Session Directory allows users to reconnect to the same session on Terminal Server clusters (Enterprise and Datacenter editions only).
21) Remote Installation Services now works for servers.
22) Active Directory in Application mode (AD/AM). An application can have its own separate instance of Active Directory which hasn't got any of the limitations that the Network Operating System imposes on the main AD.
23) The backup and restore of DHCP settings has been incorporated into the DHCP manager while in 2000 you had to change registry keys and move files manually
24) The FTP server allows different default directories to be assigned to different users.
25) There's a Security Configuration and Analysis tool to check a server's security settings
26) DNS AD-integrated zones are stored in the Application Partition of a forest so aren't replicated to domain controllers which aren't DNS servers.
27) Regedit.exe and Regedt32.exe have been amalgamated into a single utility which takes the best features of each. Both files still exist but run the same utility.
28) The DNS server has added flexibility with the new options of stub zones and conditional forwarding.
29) Internet Information Server 6 has the ability to keep worker processes from different websites and web applications separate so that if one application crashes then other websites running on the same server remain unaffected.
30) Group Policy has been improved: Resultant Set of Policy tool, 220 new templates, better folder redirection, WiFi access policy and a Group policy management console.
31) gpupdate utilty replaces "secedit /refreshpolicy".
32) There are some new command-line administration tools which are useful for automating operations on 100s of users at once.
33) New "Saved Queries" applet in Active Directory Users and Groups
34) Improvements to RRAS: PPPoE dial-on-demand for Broadband circuits, Background Intelligent Transfer Service, NAT Traversal using UPnP, improved management console.
35) Remote Storage. Infrequently used files are moved to on-line backup when disk space becomes low.
36) A new boot.ini option called "secondary plex" allows booting when a software RAID volume has failed
37) Task Manager has 2 extra tabs - one showing a graph of network usage per adaptor and the other showing details of connected users.
38) Emergency Management Services Console Redirection. Redirect the screen through a COM port so that a remote administrator can view the boot process.
39) Robocopy.exe - a Resource Kit tool to maintain identical folder trees in multiple locations.
40) Clustering service supports Majority Node Set clusters which don't require shared disk storage and it also supports multiple redundant paths to external storage such as SANs. Cluster Service account password can be changed with cluster on-line.
41) (Enterprise and Datacenter editions only).
42) Automated System Recovery is a new backup option to facilitate a server being rebuilt from scratch including recreating the partition structure.
43) Windows System Resource Manager allows limits to be placed on system resources such as CPU and RAM usage on a per-process or per-application basis (Enterprise and Datacenter editions only).
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This is a lot of changes that make 2K3 a much better program albeit not a inexpensive endeavor by no means.
Good Luck