pulling my hair out plz help

so im back at it again with this alienware d9t after returning the last motherboard i bought from ebay and trashing the one that it came with i bought another motherboard recently from ibid on ebay im not saying anything bad about them i mean they claim the motherboard was verified by eurosoft check or something thats the reason why i chose to go with them but i just got the motherboard today this morning and spent all day putting it together and double checking everything was right so i go to power it on and the same ole thing no video on the three 6800s i have and nothing on an external monitor and the subwoofer makes a popping noise for alittle while then shuts it self off but if i unplug the power and then replug it back in and turn the built in cd player on in the front that works perfectly this is driving me up the wall if this was a desktop i could fix that all day long but laptops this is crazy also if i take out the graphics card it still does the samething i mean why would the motherboard not give some kinda video atleast the bios but the screen doesnt even light up or flicker th only thing i havent replaced in the laptop yet was the ram but so far ive tried two cpu's and three graphics cards that which im not even sure work but the hdd i put in it is brand new out of the anti static bag other than that i dont know im pulling my hair out if anyone can help i would be so greatful

 

Isn't there any 'ground' connection with the chassis that must be made somewhere?
I know that on certain laptops and mobile phones, a small ground connection will prevent the system from displaying anything.
Check every connection, make sure all screws are in place etc.

 

gonna take it all apart again today see what i can see

edit:im wondering if i can just have the motherboard in the chassis with nothing else attached except cpu and see if i get the bios maybe

i found a service manual for the d900t and there pretty similar and i went through the hole thing and didnt see anything about a ground connected and its put together right fron looking at this manual

edit: i got some video just recently, the screen will turn on now but it will flash black and white anyone know what it could be?????

EDIT:i got it to boot into bios 1 time for about ten minutes, but said bios wasnt installed??but i was able to go into bios though when i press f2, also i was able to see the graphics card cpu and all the ram i had installed but after about ten minutes the screen dimmed and it went back to the popping noise.im thinkin maybe its a power problem but not sure anyone have any suggestions????