Dell Dimension 4300 won't power up

I'm working on my father-in-laws comp (a Dell Dimension 4300) that took a lightning strike through the modem. When he tried to power it up afterward, nothing happened. I replaced the m'board with a new board (exactly like the one in it originally). Now the fans work, the drives spin up and the comp POSTs. then 2 beeps and the LEDs on the back show a green 1, 2 and 3 with yellow (amber) 4. Dell's help site shows "other failure" with this configuration of LEDs but no other info. I've re-seated all cards, tried replacing the RAM and checked out all cable connections. No help. Anyone have suggestions as to what might possibly be wrong?

 

It could be an "upset" error in some hardware, like the CPU. Usually power problems like this kill a CPU. The two beeps mean memory parity cannot reset. Here is the diagnostic codes page for the dimension 4300.

 

It would seem the cpu may be damaged,have you reset the cmos jumper?also is your memory fully inserted just use one stick of the new memory,you should just be able to see the top of the brass pins once fully inserted.

At the moment you should only have these parts hooked up together

Motherboard,vid card,memory,cpu,psu and the monitor,remove anything else