this is my PC specification  
MotherBoard: MSI 975X Platinum Power Up Edition
graphic card:GIGABYTE geforce9600gt  
DDR2:4GB DDR2 Kingston  
HD: western digital 500 GB  Sata
DVD:Asus LightScribe  
Processor: Core 2 Duo E6600
my PSU is now 400 watt does it enough for this specification thnx    

Any good 500-600w PSU would be good more than enough for that I would imagine.
 
Can't go wrong with Zalman, Corsair, Silverstone, etc IMHO.

I meant to say: "Any good 500-600w PSU would be more than enough for that I would imagine."

antec earthwatts ftw!

The 400W PSU should be enough but it would run at a higher load %.
If the PSU runs hot (check exhaust) you might want to think about a more watt model.
A 600W PSU is enough for a GF9800GX2 and a 3GHz quadcore.
 
I ran my Q6600 system on a noname 550W (LC-Power green power) PSU for six months without issues.
 
Corsair VX 550W is the sweetspot of value and quality right now.
If you want to save a bit get the VX 450W.

12 volt requirements:
Figure 8 amps for the CPU
          8 amps for the video card
          2 amps for the motherboard
          4 amps for the drives and fans
 
That's about 270 watts. Figure another 50 - 80 watts on the 5 volt and 3.3 volt rails for motherboard and drive logic (5 v) and memory (3.3 v).  
 
So you NEED 320 to 350 watts WITH 22 amps on the 12 volt rail. That leaves you nothing in reserve.
 
If your 400 watt PSU will produce 25 amps @ 12 volts and it is a Tier 1 or 2 PSU, it will do. Better is a GOOD 450 - 500 watt PSU.
 
Operating a PSU close to maximum ratings is not good for efficiency, heat, and long life.

Andrius and I posted at about the same time. I need to learn to type more quickly, but at my age, that's teaching an old dog new tricks.
 
He is right. Something like a VX450 will do nicely IF you are certain you will never upgrade.
 
spuddyt: Chuck Norris' boogeyman sleeps with a nightlight.

^Agreed.

@jsc
Youth and wisdom are ...

By now the birds and the bees know what we think a good powersupply is in this forum.
Too bad nobody cares to search the forum.

@spuddyt:
Google doesn't search for Chuck Norris because Google knows it's Chuck Norris that finds you.

My favourite Chuck Norris line would be : Chuck Norris CAN divide by zero.

And the second most common topic has to be:
"I have 4 Gb of RAM installed. Why do I see only 3.25 GB?"

You shouldn't have any problem with a 400W power supply with that rig.

Based on your components at stock speed your max power consumption on the 12v rail will be as follows:
 
 
C2D E6600....................................................65w
nVidia 9600GT...............................................60w
Hard Drive (7200 RPM)..................................14w
DVD Drive......................................................14w
120mm Fan.....................................................6w
 
Total Power Consumption on 12v rail.........159w
 
Total Amp consumption on 12v rail............13.3a
 
All other components draws power from the 3.3v / 5v rails such as:
Motherboard
RAM
Hard Drive / DVD Drive read heads
Any stuck in the PCI slot
 
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Windows XP does not address more than 3.25GB of RAM. You need a 64-bit OS like Vista or XP 64-bit to access anything beyond 3.25GB of RAM.
 
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Generally I recommend Seasonic PSUs who makes PSUs for Antec (who likes to cut corners here and there), Corsair (450VX, and HX series), as well as PC Power & Cooling (Silencer series 610w and below).

Way overkill, but a gift at $119.99 after rebate. PC Power & Cooling S75QB 750W

PcP&C is the best QUALITY PSU you can buy.  You NEED 400W.  Anything less would be ill advised.  500w's is more ideal.   Crosair is also top quality.  
There are 2 Things I never recommend skimping on.  PSU's, and Motherboards, because they effect EVERYTHING in your set up.