It's dead Jim, PC help required, others may also opine.

[tw]

Originally Posted by Beest

Major symptom no activity, press the power button nothing happens, no lights, no sounds, no fans, nada.

You have two choices. Use wild speculation to keep replacing good parts until something works. Or follow the evidence to know what is wrong immediately before replacing (or disconnecting) anything. Obviously the latter costs much less money and is faster.

First, it is a Dell. So it has four diagnostic LEDs. What do those report?

Second, buy or borrow a multimeter (even $5 in Harbor Freight or a little more in Wal-Mart). The spend about 1 minute to obtain numbers from six wires should you choose that option. A next post will identify the suspect without doubts. Or eliminate over 95% of current suspects.

If you do part swapping, then the problem may be complicated.

LED says nothing about the supply. It only says AC mains power exists. And that damage can result if you make any computer changes when that light is on.