Greetings,
 
i have a problem and hope someone can help me.
 
First off my system specs:
 
AMD Athlon 5200+
Jetway 8800GT
3 GB DDR RAM
430W PSU
 
Now, i got the 8800GT about one month ago, previously it was a 8600GTS. I immediately noticed that it was barely able to fit into my pc. Still, i got the two motherboard connector (i am not familiar with technical terms) pins to snap in and connect the power unit on the rear of the card. Still, when i started the pc there was no "beep", and i am told that only a long beep  confirms that the graphics card has been correctly installed.
 
The problem i have is that i think it is under performing. When i compare the performance i have with benchmarks on some internet sites they have about 20fps more. Of course, they mostly use a besser processor, but i doubt it makes SUCH a difference.
 
I then tried running 3Dmark06, and it crashed on the third test, giving me this Error message: "IDirect3DDevice9:resent failed: Device lost (D3DERR_DEVICELOST) ". In the first two tests i got terrible fps (10-20).
 
So..I'm pretty lost at the moment. And yes, i have the newest drivers and deleted the old ones.
 
Any help would be appreciated.

Whats the brand name of your psu and what resolution do you play at?

"Sinan" is the name of the mark.
1152x864

I'm having similar issues with an 8800GT underperforming.
At this stage everyone likes to say the CPU is bottlenecking it but I think I've just hit the nail on the head with it looking like my PSU isn't keeping up.
Couple things to try in the meantime though
use driver cleaner and install fresh drivers
make sure vsync is forced off
assuming its PCIe check its running 16x

How do i check if it is running 16x?
I already tried the rest.
PSU not keeping up, hm. I saw people with similar system that have under 400W and no trouble.
 
Maybe it really is the processor..guess i'll have to wait until i can afford a new one.

Use cpu-z to check if its running 16x
 
I've just picked up a new PSU so I will let you know later if it was my problem or not.
what PSU are you running as in brand and amps on 12v rails? apparently the 8800GT is really power hungry and requires min 450W but the main problem is the amps on the 12V rails

I think your PSU.
 
Look at the label of your PSU on +12V rail supply how much Amperage?
For 8800GT 512Mb your PSU should at least can afford to supply 22A on +12V but 25A is better.  
 
Quality is better than quantity. I'd rather buy a good quality of 400 watt psu rather than 1000 watt cheap psu with the same price.

It says its 18 and 20 amps on each 12 volt rail. Its a german brand, not sure...

It is indeed 18 and 20. Hm, i read that the 8800GT is actually not that demanding, but if you say differently...

Uh, for some reason i cannot edit my message so i have to double post.
Could you recommend me a good PSU producer? Furthermore, would it be better to have a PSU that has only one 12V rail with 24A than two with 18 and 20 each?

What games do you play? And is it playing good in them? or not?

I'm using a Corsair 620HX to power a pair of XFX 8800GT Alpha Dogs and it runs fine and being modular you only need to connect the leads you are going to use. Only running one GT does not seem to produce the 'bottleneck' effect on my system (939 3800x2, 2gig Ballistx RAM) but firing up the second soon brings the CPU to it's knees in certain games.

Well, i play Crysis, Cod4 and C&C3.
 
Crysis runs at 10-20fps on high
Call of duty runs at 40-55fps on max detail with AA
C&C3 runs at ~25fps no matter the graphic detail which greatly confuses me. So on very low detail i get maybe 2 fps more than on very high. In a gamespot test they got 30fps (it's capped) with a resolution of 2048x1536 with an Athlon X2 4400+ and 8800GTS(the "old" one)
Another strange thing i have with all games are slowdowns every few seconds.

try to borrow your friends psu but a good one and test it to see if the problem persist?