Same version 3.21 problem (Win2k)! Identical error message. After several 3.21 downloads and installation attempts, restarts, registry cleaning, etc., I downloaded v. 3.20 from File Hippo and re-installed it. Works fine now. CCleaner has always worked well on this old computer. Looks like there's now a compatibility issue between v. 3.21 and Win2k.
More and more modern software will no longer work on Windows 2000, and in a few years we will start to see the same thing for Windows XP.
Backwards compatibility will make the applications bigger, more work for the developers, and more difficulties testing.
A similar thing recently happened with the latest Flash Player installer. One user found a hack to patch the installer, but that cannot really be a solution...
What was the function call used in the previous version that was replaced with WTSGetActiveConsoleSessionId() only the developers can know.
Doing a little bit research on this particular issue I found someone who is building new KERNEL32.dll versions for Windows 2000, with more functionality; see http://www.msfn.org/...ex-for-win2000/
I do no longer have a W2K machine, so I cannot test it for you. But if you want to get CCleaner 3.21 working on your system, maybe you want to try it. I strongly suggest to make a backup of your system before installing a modified KERNEL32.dll!
On the other hand I do not think that new CCleaner versions bring a lot of new functionality on W2K.
P.S. on the Japanese download site you will want at least v13i (that contains the WTSGetActiveConsoleSessionId entry point).
Where do I download v3.20? I can't find any way to access older versions from the piriform.com site.
Other third-party download sites purporting to have versions either point at piriform.com (and download the lastest version) or attempt to install adware and trojans. Not good.
Just Installed and Ran 3.22.1800 on my Windows 2000 machine -- Installed without error and Tested Cleaner, Registry and Tools all ran perfectly fine -- Great work..