i had a similar problem- its because the power computing series of computers uses 3rd party cd roms (mine is teac). this means you need a driver for the machine to recognise it- when you boot up from the cd, for some reason apples driver seems to work?? I dont know why.
what you can do is start up will the system cd in the drive, (not boot though) and take it out when the machine is powered up, and use another (should work like normal after that)
or get cd rom tookit from www.fwb.com
it has the correct extension and control panel-
if you have the original power computing system disk, you could try dragging the extension out from the extesion set that is on the disk, but i dont think it works with anything above os7.61 >> you'll need v3 or v4 of cd rom toolkit for that.