Can you get into BIOS before splash screen hang? If no then
remove all USB devices including keyboard, mouse. Try boot.
If fails the same way, unplug from wall. wait. let capacitors drain. plug in, try boot.
The HP support site has your MB doc, it has a jumper to reset the BIOS. Follow procedures closely. Try boot.
If still bad, then pull 1 memory dimm. Try boot. If fails pull other dimm replace first. try boot.
if still failing post last BIOS messages before splash screen hang.