http://www.gentoo.org/doc/en/handbook/h ... ull=1#grubThis is what I do if grub gets confused.
(hd0,0) = 1st hard drive 1st partition
(hd0) 1st hard drive MBR
Example as 0 =1st and 1 = 2nd,
European counting = ground floor then 1st floor,
USA = 1st floor=ground floor

, 2nd floor = 1st level above ground = confusing so linux counts European style.
Example:
hd7,3 = 8th hard drive, 4th partition or /dev/sdh4
1:
Boot live dvd.2:
Once logged in open terminal and type live dvd root passwordsu
passwd:
root
3:
Get partition layoutfdisk -l
Example of partition layout:
/dev/sda1 = 128mb /boot
/dev/sda2 = 2048 swap
/dev/sda3 = rest of hd = / or root
4:
Then mount partitions.mkdir /mnt/gentoo
mount /dev/sda3 /mnt/gentoo
mount /dev/sda1 /mnt/gentoo/boot
swapon /dev/sda2
5:
Get correct layout to /etc/mtab of partitions.grep -v rootfs /proc/mounts > /etc/mtab
6:
You can either use grub-install or grubgrub-install --recheck /dev/sda
grub-install /dev/sda
ORgrubgrub> root (hd0,0)
grub> setup (hd0)
What happens here = grub-install --recheck /dev/sda
This will check current config or 1st hard drive.
grub-install /dev/sda
This will install to 1st hard drive MBR grub according to "grep -v rootfs /proc/mounts > /etc/mtab"
or listing as is now in /etc/mtab so /etc/mtab = auto genenrated = should be good.
7:
Now check /boot/grub/grub.confnano /boot/grub/grub.conf
Example:title Sabayon Linux
root (hd0,0)
kernel (hd0,0)/kernel-9.4.2500 root=/dev/sda3 vga=791 volume=1% res=1440x900 xdriver=nvidia eth=xxx dodhcp and-alot-off-other-options -or-cheat-codes-as-you-feel-is-good
initrd /something-something-something
title Windows
chainloader+1
8:
If good then press ctrl+x to exit or y or n to yes or no for save and exit.
9:
Reboot
Most of the time the errors you can get = Houston "/boot" where is she, we can not find her, did Mr. Scotty beam her up to the enterprise arrgh.
Or
grep -v rootfs /proc/mounts > /etc/mtab
This one writes known or mounted to /etc/mtab and how what and where that is important for grub to figure out what is going on so it can do the install.
If /etc/mtab is empty or confused then grub will be confused but might still work during grub install.