In my experience for every reader or post one might see on a board such as this - there are likely 10s or 100s that are in the same boat but do not post.
This was a decision Piriform made.
Still considering that there are alternatives still supported then this thread can best be utilized by readers if over time those still requiring a Win2K version to comment on their experience with other systems and hopefully the 2nd best alternative to using Defraggler for a Win2K system can be arrived at.
My take.....
To bad, the current version doesn't support windows 2000. I too have this OS and was trying to update it from the one around June 2010. I just downloaded the last one supported for w2k as v1.21.209. I also have all of these OS', W2K, XP, Vista, Win7 and MACOS. Moreover, non-of my computers are connected to the internet so security issues aren't a big issue. They are used for old and new application development and interoperability testing for apps that need to work together in a multi-MSoft OS environment. Now, for Unix and Linux... that is a different issue and piriform doesn't support the Unix's.
Be aware that piriforms'other software products still support to this day windows 2000. I.E. Recuva, and CCleaner thank god!! Just not, Defraggler. Hmmm.....!