Reinstate GRUB in MBR as default bootloader

[Barry Yu <barryyupuilee@xxxxxxxxxxxxx>]

My system is a dual boot FC3 and XP, the default bootloader was GRUB and 
installed in /dev/hda, displaying a menu for option of  FC3 and 
Microsoft. The XP was corrupted and I rebuilt the boot.ini file, since 
then the M$ bootloader became default and I left with option to use DOS 
and XP on that menu - there was no FC 3 bootup built in tha M$ menu, I 
tried to re-instate the GRUB into MBR like this;

Booted up the rescue CD and enter : linux rescue
chroot   /mnt/sysimage
grub-install    /dev/hda
(I tried above on other machines before in several times and worked fine 
but not this time - see message displayed below)

A message displayed ; /dev/hda does not have any corresponding BIOS drives.
The result was I can't bootup the GRUB.
So I booted up the rescue CD again and get into recue mode;
chroot   /mnt/sysimage
grub-install  --recheck  /dev/hda
(Displayed below)
(fd0)   /dev/fd0
(hd0)  /dev/hda
(hd1)  /dev/hdb

And the I rebooted sytem, this time GRUB is reinstated and worked O.K.

My question; Why GRUB was corrupted (?), why grub-install /dev/hda won't 
fix the problem but grub-install --recheck /dev/hda would?