lee wrote:
Thanks and I did my numbers:

I'm thinking a P4 9xx CPU and it draws around 100w alone, new display cards
(ATI x series) also draws a lot of power. More than 1 web site said hard
disks draws 25w so I use that in my calculation to be on the safe side.

Don't believe 'more than one website'.
Look at the specs for your drives.
The makers website will list exact startup currents.