I've come to the conclusion that the problem is with 3DMark2000. I ran Final Reality and my scores are very similar to those in Win98. I also played a couple of games and the extreme frame rate choppiness that I experienced in 3DMark2000 was non-existent.
FYI, I just went to Windows update and it looks like Microsoft has certified the Nvidia 5.32 driver for WinME. The 5.32 drivers are a download on the Windows update page now.