Mac OS X* (v10.1 or later); Universal Binary
Windows 98, 98 SE, Millenium Edition, NT4, 2000 Professional, XP, Vista
You will need to have QuickTime installed to use RiddleMeThis. You can obtain QuickTime here.
RiddleMeThis does not use extensive system resources and should perform well on older hardware, but if you make extensive use of images and video you may need a decent amount of RAM.
* Mac OS Classic is no longer supported, but I continue to provide old versions of RiddleMeThis which do run on Classic. I no longer have the ability to test new versions under Classic.