Weird PCIE Power Problem

[thefear]

Hey guys im stuck with a pretty interesting and frustrating problem..

Heres the story,
Last night when i went to bed i turned off my computer as always, and then earlier today i tried switching it back on, and nothing happened. the computer seamed to switch on for a microsecond then switch off again,

after a few hours of playing around trying to work out why this is happening and possibly toasing my 9800GTX card, i found out that my computer boots up only when the PCIE Power cables are not connected to the card, when they are connected the computer turns on and off within a fraction of a second (Sorta like what happens when a shortcurcuit happens).. So im stumped to know why this is happening, i also dont get any output from the graphics card to the monitor so i cannot see anything on the screen, And im very sure my motherboard (Gigabyte MA790X UD4)does not have any kind of onboard graphics either,so i cannot understand why the POST passes?..

Could it be coz my graphics card is toast?.
I have tried it out with another graphics card (7900GT) and the same thing happens, no go with the PCIE Power connected.

I have used this computer flawlessly for a good 10 months and had no troubles so im sure its not a compatability issue (nVIDIA Graphics in a ATi Board)

So any help in helping me sort out my problem would be greatly welcome..

Thanks a load dudes, i hope yas understand what i mean hehe

 

[thefear]

any ideas dudes?

 

[viper200]

have u tried
http://images10.newegg.com/NeweggImage/productimage/12-189-120-02.JPG

see if it lets u then?

 

[thefear]

nup they dont work either. it does the exact same thing by shutting off really quickly

 

[whatwave]

Try a working power supply out of another system...sounds to me like your power supply just can't handle the extra draw from the video system either due to age or a problem in the power supply.