As above, this is a better PSU http://www.ebuyer.com/UK/product/114931 Antec true power one

Also,

Does that P4 chip match this : Designed for Intel® LGA775 processors with1066/800MHz FSB
Supports Intel® Core™ 2 Duo(Extreme Edition) & Pentium® Extreme Edition & Pentium® D & Pentium® 4 Processors

Could possibly be one of the ram sticks, I'd disconnect all hard drives / cd rom drives, and power it up, you could also take the cmos battery out for a few mins and put it back in and boot it up, see what it say's, bit of trial and error unfortunately m8