I just got my mahcine setup to dual boot Windows XP and Gentoo, I had a bit of a hard time getting grub to work right mainly because I wasn’t coming across the information that I needed to get it going. So here is my machine info in hopes that it might help some others.
hda1 – Windows XP
hda2 – /boot
hda3 – swap
hda5 – /
hda6 – /home
hda7 – /mnt/share0/
hdb1 – /mnt/share1/
Grub.conf – I have it default to start Linux
title=Gentoo Linux 2005.0 – Default
kernel /bzImage root=/dev/hda5 udev
title=Windows XP Professional SP2
When I installed Grub I did it like so
grub> root (hd0,1)
grub> setup (hd0)
That got it working for me. Now when you reboot you should have grub ask what OS you want to boot into. They should both work at this point. I did read somewhere that you should have SP2 installed before you dual boot as it tends to rewrite the MBR. I cant confirm this as I made sure to install it before I installed Gentoo/Grub.