Gradient Overlay

i know how to make a gradient overlay, but i can seem to make a custom one, i can only use the presets, so, how do i make a custom one?

not sure what photoshop you're using, but in cs, you can just click on the gradient image (not the little down arrow next to it) and you end up in a little gradient editor window, in which you can rename the gradient and click "New" to save it as a new gradient.
you get these little arrows to play with and move around to define the gradient.

have fun,
puck

thanks!