making a grub boot floppy, as simple as:
# cat stage1 stage2 | dd of=/dev/fd0
Files "stage1" and "stage2" are usually present in /boot/grub directory.
It will allow you to have a grub prompt on boot.
From there you can specify your boot parameters:
grub> root (hd0,1) => it is the partition containing the kernel. (hd0 = first disk,
1 = second partition).
grub> kernel /vmlinuz-xxx ro root=/dev/hda2 => note that once you specified the correct root device above, the completion should work to find the correct kernel (ant it is a good way to verify). Grub is able to read directly most filesystems. The ro is normal, it means to mount the root filesystem readonly first during boot (it allows to fsck the filesystem if needed), but it will be remounted readwrite after. The root=/dev/hda2 argument is the device to mount as the root filesystem. It
can (often) be different than the one specified in the root (hd0,1) argument.
grub> initrd /initrd-XXX => if needed. It is a tiny "embedded" filesystem usually containing special drivers needed before accessing harddrives (like SCSI or RAID drivers). Again you should use completion to find it.
Now you can boot the system on your harddrive, type:
grub> boot
you can also choose to re-install correctly Grub on the disk if the disk comes from an other computer or the configuration was incorrect:
grub> setup (hd0)
A lot more info is available at:
http://www.troubleshooters.com/linux/grub/grub.htm