Windows 2000 Professional Microsoft released this new Windows version 5.0, Build 2195 in February 2000. It is the desktop operating system of the new Windows 2000 platform for x86 architecture and be completed by the versions Windows 2000 Server, Windows 2000 Advanced Server and Windows 2000 Datacenter Server. As a minimum requierement for the installation a Pentium processor, 32 mbyte main memory and 650 mbyte of free hard disk storage are needed. Microsoft had planned to develop also a operating system version for the Alpha architecture, the plans were stopped after an announcement of Compaq. Compaq restricted the support to Windows NT 4.0 with service pack 6 and not higher at 1999-08-25. Microsoft stopped the development plans for the Windows 2000 32- bit of Alpha version after that. Windows 2000 unites defined roughly the user-friendliness, pug & play and USB device support of Windows 98 and the safety and stability of the Windows NT family. The update to this new operating system is possible from Windows 95, 98 and Windows NT 3.51, 4.0. It is a multitasking, multiprocessing operating system and supports up to 2 processors of the x86 32- bit and 64 bit architecture with SMP. Threads or processes can choose between the available processors. Beside the complete revision new features and many improvements are integrated. The result is high compatibility, simplified administration, increased hardware support with over 7,000 devices, file administration and extended security functions. Applications for Windows 9x are only supported restrictedly. The installation is possible from CD-ROM or over the network from a file server. The virtual addressable storage is 4 gbyte and is managed by the Virtual Memory manager (VMM). VMM assigns the addressable storage on the actually available physical memory and the memory page file (pagefile.sys) on hard disk. The field of application of this operating system is suitable as a single user computer or as a client in company networks. The operating system is enhanced with the game interface DirectX 7.0, the Internet Explorer 5.0 made access to the Internet possible. Windows 2000 authenticates the user first at the access to files, printers or other computers. Networks are supported with the protocols TCP/IP, NWLink and AppleTalk. Windows 2000 supports the data interchange in decentralised working groups and central domains. Furthermore the Registry consists as in Windows NT 4.0 before of the system files SAM, SECURITY, SOFTWARE and SYSTEM. The hierarchical database saves information of the hardware and applications as well as configuration settings. The following basic services are in Windows 2000 Prof. installed. The SFC (System File Protection) offers protection from overwrite of Windows system files. It is possible to create hardware profiles for different hardware configurations with the settings of all devices and services. NTFS is used as file system in the new version 5. The specification of user rights is possible for files and directories on file system level, file compression in real time, disk storage quotas (Quotas) and encrypting with EFS (Encrypting File System) can also be used. At the specification of rights the Access Control List (ACL) is stored with every file and every directory. The compression and encoding exclude each other, only one of the options on the same object can be used. Furthermore the FAT/FAT32 file system is supported. Windows 2000 Prof. is also suitable for mobile use on notebook computers. With the complete support of the technologies APM and ACPI an effective energy management and thus lower electricity consumption is possible. With the Suspend to Disk function the computer can be put into a power saving mode and is in the same condition as before after short reactivation time. An assistant supports the user at the administration of the network connections, with use of VPN (Virtual Private Network) and IPSec (Internet Protocol Security) secure mobile access to company networks is possible. The printer administration was simplified with an assistant. 2004-02-13 announced Microsoft that parts of the source code of Windows 2000 has leaked on the Internet. The source code appeared illegally in peer-to-peer file sharing networks, Microsoft said to use the full law to protect the stolen property. 2003-06-25 the Service Pack 4 eliminates 675 bugs appeared since the last service pack. New is the support for USB 2.0 device connections. - unattended installation of the operating system via script possible - different options for Windows start like "safe mode" and "last as good known configuration" - booting from the Windows 2000 CD-ROM offers repair of the operating system or recovery console - supports the display of the desktop on up to 10 monitors - task planner for time controlled executing of programmes - utilities for hard disk like defragmentation and check on disk errors - event viewer for protocolling of application, security and system events - backup tool for data safety and recovery - Microsoft Management Console (MMC), administration of the local or remote computer, expandable by SnapIns - support for local and predefined user accounts, domain user accounts - ActiveDirectory directory service available if client is member in Windows 2000 domain - New protocols for a secure authentication in the network are EAP, RADIUS, IPSec, L2TP and BAP