There is a System Preference Pane for that mouse which configures the various pressure points on the body.
This pane now comes with the OS but on your older PPC iMacs and eMacs, this pane may not be there. That would allow the mouse to operate with Right and Left clicks because there is nothing to turn it off.
The bottom line is that the Sys Admin could have disabled the Mighty Mouse, maybe not deliberately, and only allowed it to function as a single button mouse.
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I'll say straightaway that I'm a PC person. I don't despise Macs, but i prefer PCs. In any case, my high school yearbook is completely Mac, so I have to use them whether I like it or not.
We just got several (~10) brand new iMacs in our room, replacing mostly eMacs and a couple PowerPC iMacs. Although they came with Mighty mice, the new macs do not recognise a right click. However, if i take one of the mice and plug it into one of our eMacs, running an earlier version of OS X, it is possible to right click with the mouse. Why is this? Our system administrator seems to have configured all the macs to restrict almost everything that isn't absolutely for yearbook (and some applications that are, such as word), so is it possible he disabled right clicking with the mice on the machines? We can right click with any other mouse we have, just not the Mighty Mice on the OS 10.4 machines.

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