Re: Motherboard fan headers
Check the amp rating of each fan and locate the fan connector details in your motherboards manual.
My Asus P5KC manual states the following, but yours will be different:
"The fan connectors support cooling fans of 350 mA~2000 mA (24 W max.) or a total of 1 A~7 A (84 W max.) at 12V.
The first figure applies to a single header, as it assumes you would only connect 1 fan to it (I use a cable splitter to attach more though).
I run 8x120mm fans through the motherboard headers, totally about 4 amps at full power.