Correct syntax for mkinitrd command?

[Andrew Konosky <TerranAce007@comcast.net>]

I am trying to compile a vanilla 2.6.9 kernel and I have configured it 
and compiled it, but the mkinitrd syntax is different from the one I am 
used to in Fedora. My kernel modules are in /lib/modules/2.6.9custom and 
I want to create an initrd image in /boot/initrd-2.6.9_custom.img.

I ran this and it created an initrd image, but when I boot I get a 
kernel panic because the root f/s cannot be mounted:

#: mkinitrd -k -o /boot/initrd-2.6.9_custom.img -r /dev/hda4 2.6.9custom

What is the correct syntax for the command then?

Also, I use an ext2 root partition and have that compiled as built-in 
instead of a module, but which device drivers do I need to compile 
built-in so I don't need an initrd image? Just IDE, or do I need 
northbridge, southbridge, PCI & USB controllers, etc...?