One of the hardest things to do is troubleshoot a box that don't boot.
I have a tool and software that I use that reads post codes as a box boots. It will tell me exactly where the stop error is. It sounds like the led does basicly the same thing. You should get different sets of numbers as post progresses.
Before I had this I would pull out everything but one stick of good memory, the graphics card, better off with onboard vid here or pci vid, agp cards in older motherboards can be the main cause of boot problems.
Since the cpu fan spins up we can rule out anything power related.
If all your components are good then I would bet you have a dead cpu. It also could be the board. Check the etchings around the heatsink. Due you see any scratches anywhere?
If you do then chances are the board is dead. If the processor is good, tested in another working board, then the board is the problem.
Also make sure you have the jumpers set correctly.