Stays on for only 5 seconds(arrr)

I have a HP ze4420us with an AMD chip.
The problem is that when i turn it on it only stays on for 5 seconds (exactly) then turns itself off. Every now and then it will go to the screen where it says press F2 for setup or ESC to change boot order, but after that it wont stay on long enough. I have changed mobo, power supply, and the chip works fine on my desktop. Even if i unplug the hard drive the BIOS should still load right?

Any help appreciated

 

Did you check the Memory....... Run [link=http://memtest86.com]Memory Test V3.2[/link] overnight and see if you come across some errors...

 

i cant, i turn the power button on and after 5 seconds it turns off, it doesnt even get to the start up screen where it runs the POST and what not... I have changed almost every component...im throwing it away lol

 

Does it incudes the RAM as well?

 

Check your CPU cooling. From the way it sounds, either your CPU cooling isn't attached so that it's making proper contact or the cooling fan isn't plugged (or broken).

Also, does this happen with the unit plugged into the wall or when it's running off the battery, or both?

 

yea, i guess i would just toss it but i know the chip and mobo are good and the memory is new.....im stumped....maybe i will take it in somewhere

 

yea i noticed that when i turn it on the fan doesnt move at all, so i had an extra one and same thing, wouldnt budge. the fan shoudl turn on instantly right?

 

Yeah, should, unless there's some thermal control, but even then, it should kick in. Laptops don't have a whole lot of room for heat disappation.

 

Also check to make sure if there is any loose connection...
Remove the battery and switch it on with direct line..

 

maybe the battery has bit the dust and can no longer hold a charge?

 

yea i exhausted all of your options but with no prevail....im just gonna put it in my closest till i get time to take it in..thanks anyways for all the suggestions

cheers