My monitor goes black when I start up games

I have just been built a new comp but my mums boyfriend, he has put an Nvidia geforce 6600 graphics card on an amd athlon 64 3700+ ..
I got it yesterday with nothing but the nvidia drivers on it, I installed a game which is fairly good graphics wise and it played, perfectly except a little lag, but when I installed counter strike source and went to play it my screen goes blank just when the menu comes up for css.

and thats it , the screens on but it says no video output, so I have to restart my comp,cus ctrl alt dlt doesnt work or the escape button,

I have made sure that the monitor is plugged in to the wall and not an extention, it is a single wire with a plug , no power supply thing,

it might be that I have installed something which has messed this up but I do not know what , as I am "OK" with comps I dont think it could be adobe flash or java or anything like that, definately not utorrent, and there is no power supply plug on my geforce 6600 for the fan either so..need helpPP!P!PP!
 
That 250 watt PS may not be enough watts to play many of today's games and support that video card
 
Did u check to see if the video card is compatible with your cpu? You know that nvidia geforce cards are made for intel cpu's not amd. For an amd cpu, u need a hd radeon video card.
 
Did u check to see if the video card is compatible with your cpu? You know that nvidia geforce cards are made for intel cpu's not amd. For an amd cpu, u need a hd radeon video card.


Not really I have ran my GeForce 550 ti with my Amd x 4 cpu now for a year with no problems, Plus if this was the case I do not think they would put nivida graphics on mainboards that support AMD CPU. It is more of a power supply issues as Tmagic has stated
 
Did u check to see if the video card is compatible with your cpu? You know that nvidia geforce cards are made for intel cpu's not amd. For an amd cpu, u need a hd radeon video card.
I have never heard of this, and I believe this is false, misleading information
 
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