External USB drive problem

I have put a new Western Dig 40 GB drive into a Sony CD enclosure (usb1). The drive has been initialized. When I plug it into a friend's Mac running 9.2 it pops up on the desktop like any good normal drive should. Worked on 2 different machines.
But when I plug it into 'my' iMac with 333 G3, 288 ram, running OS 8.6,....nothing happens.
Any ideas???

Could the problem be your older version of "OS 8.6"? It may not have the capability of the newer "9.2".