Sorry, you need a new computer. The Bondi iMac is just too old, with graphics and a processor too slow (even after the upgrade). Running Medal Of Honor on it is an exercise in futility. Even if you do get the application to start running, it'll go too slow to actually play. You can't upgrade the graphics (except to use the now-rare 8MB Voodoo2 Game Wizard), but even that is too slow to work.
To put things in perspective, even my 1 GHz eMac choked slightly on that game. And that eMac was probably at least three times faster than your iMac.
If you really want to run Medal Of Honor, though, you could buy a GameCube and get Medal Of Honor for that. GameCubes are cheap ($100 new, $70 used), and all the games run smoothly on them and are really fun. The older Medal Of Honor game is $15-$20 now, and the newer one (Rising Sun, located in the Pacific instead of Europe) is $50 because it's brand new.
EDIT: Changed the wording slightly to reflect the fact that you have a G4 upgrade. It still doesn't change the message though - the upgrade helps a little, but the Rage IIc in the Rev. A iMac will never be able to run modern 3D games well. Even the Rage Pro on the Rev. B, C and D iMacs will not be able to run it. The minimum to even start the game would be a 600 MHz iMac with a 16 MB Rage 128, but that would still run slowly. If you want good performance, you're looking at a new eMac or iMac, or a G4 tower 733 MHz or faster. Anything less will not run the game well enough to be worth playing.