Hey Piriform! Love Speccy!
I recently had someone who uses Windows Milennium Edition almost exclusively (Don't Ask), try Speccy on their PC to see if it worked, because Ccleaner I know works in Win9x/Me.
When he first initially started it up, it gave him an error of a missing WINHTTP.DLL file. After pulling this from a WinXP install he had on another PC, it worked fully for him, with no problems, it seems.
Although Win9x/Me is outdated and now at its end of product life as of a few years ago, I thought I'd bring this to your attention, if you already didn't know about it, that it works.