My disk structure on sda is as follows:

sda1: windows
sda2: boot
sda3: swap
sda4: root

I've put the kernel files on both my boot partition and root partition.

When installing grub in command line, I did:

root (hd0,3)
setup (hd0)

my grub.conf is:

title=gentoo
root(hd0,3)
kernel /boot/kernel-2.6.18-gentoo-r4 root=/dev/sda4

title=xp
rootnoverify(hd0,0)
makeactive
chainloader +1

My windows option boots just fine

When I boot Gentoo, I get the following:

VFS: Cannot open root device "sda4" or unknown-block(0,0)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

I get the same thing when I use in grub.conf:

root(hd0,1)
kernel /kernel-2.6.18-gentoo-r4 root=/dev/sda2

and ran setup (hd0,1) instead when installing grub.

The part that makes no sense is that it is trying to mount hte fs on block (0,0) when I am never specifying (0,0) or sda1 anywhere. If it is looking on that partition somewhere, that would explain why it wouldn't boot since it's not going to find the kernel on the windows partition.

This error means your kernel cannot handle your SATA controller. You left out SCSI support and/or support for your SATA chipset when you configured your kernel.

Try this.

(1) Press "c" key on seeing the Grub screen and drop into a Grub prompt.

(2) Boot Gentoo manually with these lines
(3) Report which line Grub doesn't like and the error message. Pay attention to the parts marked red

Also are you sure your Gentoo has no initrd file? Don't run Gentoo myself but only its variants.

In a Grub prompt to reboot just type
To see what other commands available type
To go back the original Grub menu type

Emerson got it

I went back and compiled all sata and scsi support into the kernel and now it works fine.

Thanks.