If somebody knows about this problem please help me. I am running a P4C 2.8GHZ HT with 800 FSB 400MHZ DDR memory and FX5600 128mb 128bit 8X VIVO with a 4X AGP capability of my board.

the problem is when i start my computer the graphics card software promts a warning message that the NVIDIA SENTINEL detect that my graphics card is receiving not enough power, so its performance is being reduced to function properly.

It confused my because the GeForce FX's ULTRA versions and something like FX9xxx are the only graphics card in Geforce FX family that supports additional power supply.

Can somebody help me bout this?

MY SYSTEM IS:

Intel Pentium 4C 2.8 HT with 800 FSB
Asus P4PE-X/TE with 4X AGP, supporting HT
512mb DDR memory with 400mhz FSB
GeForce FX 5600 128mb 128bit 8X VIVO
Seagate 40GB 7200 rpm
400 watts power supply
1 CDRW drive
1 DVD drive
1 FDD

That is strange? As long as your power supply is not going bad. You should not be getting this msg. Can you tell if the performance is really suffering? or is the msg being mis-reported? Could be during bootup the cpu is being tied up doing other calculations before the video. causing an incorrect msg.
look for " bootvis " it's a free internet download program monitor that can monitor bootup and report where most of the bootup sequence is being spent. It can also streamline your bootup and that may fix it? Try it.