|In your original post, the only thing you said that could be construed as an answer to my specific question was "I've tried reinstalling original memory but nothing." Your most recent post is much more detailed and certainly expands on, "but nothing." Especially point #3, which you didn't mention in your OP. So thank you!|
That being said, here is an explanation of those four diagnostic lights: http://support.dell.com/support/edocs/systems/dim4550/advanced.htm#1118998.
It does appear that you may have fried something since those lights don't light up at all. You've already tried reseating everything, but it might be worth doing that again just to be sure. There are some specific instructions regarding that on the page I linked above. Good luck!