Yes. I still use W2k. A month or so ago I added a new W7 64bit which impresses me as the real next generation after W2k. Everything just seems to work; set up with the Windows Classic desktop I hardly notice the difference. One difference is important: the security setup on the W7 machine inspires confidence even without the additional tools I have added; and, also, things like the fact that I cannot update the I.E. browser to the latest version are impediments to web development. I still use W2k because it is so highly customized to my work and also because a large number of small things are not compatable with W7. What I have also done is to install VMWare Workstation with a W2k Virtual Machine for many of the same reasons. Hopefully at some point I will be able to once again work on just one machine and keyboard. (Two keyboards, a mouse and a trackball have me trying to cut and paste from one machine to the other, wondering why the use of the mouse/trackball has stopped functioning, etc.) A tablet (not a pc, a pen thing for use on Photoshop images) which is incompatable with a i7Q4 processor and motherboard but which is important for what I do is another reason I keep the W2k box.
I see I must also keep the old version of HTML Validator for use on W2k if your support is to be discontinued on later versions.