When I asked if a 10 year old operating system such as Windows 98 was still an option as a desktop operating system for business today, many TechRepublic members argued (quite rightly) that although Windows 98 wasn't a viable choice, Windows 2000 Professional certainly could be. Others added that Windows 2000 Pro was their favorite version of Windows.
Jason Hiner and I were discussing this exact point yesterday and came to a similar conclusion- Windows 2000 Professional might have been the best desktop operating system that Microsoft produced, up until XP SP2 shipped.
What about everything else Microsoft made?
Arguably MS-DOS 5.0 was probably the most stable and efficient operating system Microsoft ever made, but DOS's usefulness is long past. Any version of Windows before 3.1 was an interesting toy, but not very useful. Windows 3.1x was usable, but if you looked at it cross-eyed it crashed. Windows 9x was built on an architectural house of cards as the final version, Windows ME, proved beyond a doubt. The various versions of NT Workstation, from NT Workstation 3.1 (really 1.0) through 4.0 (really 3.0) were OK but limited by hardware restrictions and software incompatibility.
That leaves Windows XP and Vista. There's no reason really to pile on where Vista is concerned. Although on new hardware Vista's a half-decent operating system, everyone knows how it has turned out. When XP first shipped, it was slower than Windows 2000 Professional and more unstable. Until Microsoft shipped Service Pack 2, XP really wasn't that great.
What makes Windows 2000 Pro so great?
Windows 2000 Pro shipped February 17, 2000. It was a direct descendant of Windows NT Workstation 4.0. It overcame a lot of NT WS's limitations by having a wider hardware compatibility list. It added Windows 9x features such as USB and Plug And Play support. Its minimum hardware requirements of 64MB of RAM and a 133 Mhz CPU were well below hardware that was being shipped at the time, so it ran really well on just about any machine you threw at it. There was no heavy GUI sitting on top of it, so response times were almost always fast. It also included an Application Compatibility kit that allowed more DOS and Windows 9x software to run on it than could run on NT Workstation.
Windows 2000 Pro isn't perfect of course. There was no built-in firewall, which made Windows 2000 Pro more vulnerable to some viruses and worms such as Code Red. Not all hardware vendors embraced Windows 2000, which meant that older hardware would never run on it. Its default configuration left security as an afterthought.
One nice thing 2000 Pro lacked which showed up in XP was Windows Authentication. This makes installing and reinstalling Windows 2000 Pro much less of a headache than XP.
As I said to one TechRepublic member's chagrin, Windows 2000 Professional never gained a lot of traction in many business environments. In October 2001, when XP shipped and 2000 Pro had already been out a long time, Gartner estimated that Windows 9x still had about 80% of the installed base of PCs. Windows 2000 Pro only lasted 18 months before Microsoft shipped XP. That was too fast of a turnaround for some businesses that were already on Windows 98 and had ultimately decided to sit out 2000 Pro while waiting for XP to ship.
Microsoft stopped mainstream support of Windows 2000 Pro with Service Pack 4 and one Security Rollup Package. You can't get new software from Microsoft such as IE 7. That's not to say that you're stuck if you decide to use Windows 2000 Pro on an old piece of equipment however. You can still put a modern Web browser such as Firefox on it. You can also patch some of the security holes in 2000 Pro by putting a virus scanner and firewall such as ZoneAlarm on it. Microsoft will also continue Extended Support on Windows 2000 Pro until July 2010 which means that it will continue to create security patches for 2000 Pro until then.
The best there is, the best there was...
Windows 2000 Professional may be long in the tooth, but it's still a good choice for older equipment. It does infinitely more things than DOS. It overcame the hardware limitations of NT Workstation. It was way more stable than Windows 9x and could run almost all of the same software. It wasn't encumbered by the restrictions or the hardware overhead of Windows XP and Vista. With some added software and configuration changes, it's relatively secure. In short, Windows 2000 Professional may be the best desktop OS Microsoft ever shipped.