How to tell what power supply you need

[Padarathsean]

Hello,
I just need to know what kind of power supply I will need.
Here are the specs:
Pentium D 3.2GHz proessor
MSI inlet l945GZ MotherBoard
3 GB DDR2 RAM
250GB and 1.0 TB hard drive
1GB radeon HD 4550 graphics card
Samsung 22x DVD-RD IDE

 

[mosox]

Not much, 400W is fine. What's your budget?

 

[deadlockedworld]

On a computer that old you dont want to invest more than needed.

Antec 350w
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371003

Corsair 400w
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139017
(Corsair rebates are generally more trustable than many companies-- so this really will be $25)

 

[Zenthar]

For power supply needs in zones I'm not too familiar with, I usually use a PSU calculator.

 

[joefriday]

a decent 300w PSU is all that's needed with a bit of room to spare. Peak power consumption on a rig like that would be approx 200 watts, due in large part to that Pentium D.