I've bought and repaired quite a few broken pcs over the years, and anytime it's an Alienware that's not starting up it usually means the motherboard has burned out and usually taken the CPU with it.

Mostly because they use the intel stock cooler on an i7 and then make that singular fan also pull double duty as exhaust in an itx sized case, without having heatsinks on any of the vrm or PSU components.