it is more likely you chose to install grub to a partition rather than to mbr.
I caution you not to install grub into SATA until you have tested pata. that way you can change the bios boot back to sata if grub fails for you.
Also research how to backup your SATA or repair when you do install grub.
as that means we want bios pata then sata it changes your menu.lst or /etc/grub.conf file Do you see what I mean?
ie when you change your bios again, you need to edit your menu.lst grub file to change the hd info
OR you have to change your device.map file which is easier.
2) when you say the entire drive do you mean you have only one partition and no swap partition?
3) do you have a boot disk to get into linux?
read this if you have time to give you an idea of the structure of your menu.lst/grub file
I prefer commands to install grub as you get responses.