Are you sure the hard drive was formatted correctly? Just a suggestion. PPC Macs must be formatted in the Apple Partition Map Scheme in order to boot. PPC Macs will not boot from a GUID Partition Map Scheme. You will be able to install your OS on the hard drive but it will not boot. When formatting your drive in Disk Utility select the Options button and then select Apple Partition Map.

One thing that you said stands out to me. That is "front LED comes on" If the sleep indicator light comes on and stays on there is likely a problem with your logic Board. However it could be just a connection. I have had this problem before myself. Here is an excerpt from the service manual that may be helpful. 6. Boot up the system and check the sleep indicator. If it turns on solid and turns off, the main logic board is getting power and completing the boot cycle. If no video appears, there is an issue turning the video turn-on or system software is corrupted. Try booting off the Mac OS X Install DVD. If the light does not turn off, the boot cycle is not being complete. This may be cause by the hard drive not being seen by the system, system software corrupted or possibly a hardware issue. 7. Press Caps Lock key to see if key light comes on. If it does, hold power button down for six seconds to shut down the computer and restart. 8. If it still doesn’t start, verify power button cable is connected...