How Big a Power Supply Do I Need ?

I am planning on building a system with following configuration & need to know how big a power supply ( in Watts ) do I need.

P4 Dual Core 3.0 GHz

2 SATA Hard Disks 250 GB Each.

One DVD ROM

One DVD Writer

Dual monitor Card for two monitors, one 21 inch & one 17 inch

2.0 GB DDR2 RAM ( 533 MHz )

Please suggest the specs for a power supply, especially Watts.

Thanks
Mike

 

400W should do it fine, possibly 480 to be on the safe side.

 

I would go 550w incase you want to add stuff later on=),Get an Antec.

 

I second what mcadam said as long as its quality brand,if your gonna add a powerfull video card a 7900 for example consider a 500 or 550 as sewy said,other good brands are Enermax,ultra,Tagan,thermaltake,coolermaster,ocz

 

Might I add to that list Rikky, Hiper make brilliant PSUs.

 

I'd recommend 500 watts, your card might make a significant drain on the psu.

Scout353

 

What matters Most isnt the total watts of a PSU but the amount of Quality +12v amps, you should look for a PSU that can provide Minimun of 28, +12v amps on th 12v rail or a total of on a multi rail PSU.

Here's some reading
http://www.extremeoverclocking.com/articles/guides/Power_Supply_Guide_1.html

I'd suggest a OCZ 520w Powerstream (they also sport a 5yr warranty)
http://www.newegg.com/Product/Product.asp?Item=N82E16817711002

 

i recommend getting the seasonic S12-600 600W PSU.