First an update: I have not been able to get the HHMI Virtual Labs disk to work under Mac OSX or Windows. Granted I'm not the most adept Windows user, but I can't even get the computer to recognize that there is a program on the disk. Too bad because the splash page looked pretty slick.
On a more positive note: The disk of supplementary material that came with the NIH science unit works well under Windows and presumably under Mac OS9 (it kept trying to open OS9 under my OSX browser). It has lots of good stuff on it, including a short documentary on what a hazmat worker does. We'll be trying out the Toxicology unit in the next month since Xavier has finished his 6th grade science course. :D