Okay - If you don't have it then please go get it - it is check install - is is easy to use and makes life much easier when a little mistake is made, and it makes nice slackware packages too.
after you have checkinstall, or if you decided to he** with pbharris, i don't need no stinking checkinstall then run make install tehre is an isntall scrpit, for the source it defaults to installing here:
/usr/local/sbin/grub-install - try running it as root and you should be on your merry way.
btw - here is pretty close to what i would make your grub.conf look like, you wopuld need to create the initrd images:
i am not sure of what i would put in for the vga stuff....
kernel /boot/vmlinuz ro root=/dev/hda4 hdc=ide-scsi
kernel /boot/vmlinuz-2.4.20pre5 ro root=/dev/hda4 hdc=ide-scsi