I googled a little and realized that E. Roshal supports no more Windows 2000 by new WinRar releases. But Tcmd does, moreover - Tcmd has wide Windows support starting from Windows 95! It´s all about proper unrar.dll library spreaded together with Tcmd. The current one is wrong, some procedures can not be handled by older OS (Windows 2000)

http://forum.altap.cz/viewtopic.php?f=6&t=7464&p=27961&hilit=windows+2000+unrar#p27961
(Czech language only with some screenshots)
I know that the market share of Windows 2000 is not huge at this time but for sure larger than market share of Windows 95 or 98... And finally: Tcmd claims that support all Windows from 95 above - or not?
As I am not geek, I have no clue how technically difficult can be the releasing of patched library. But I downloaded and tested the new Altap Salamander file manager with bundled unrar library under Windows 2000. It works on all WinRar archives with no flaw.