Grub will be installed if Everything is chosen by Custom Installation at the time of installation.

grub can also be installed with the following command:

# mph-get install grub 

Note that LILO or any other boot loader will not be overwritten by just installing grub. So rest assured and install grub in your system.

Perhaps it is uneasy to install grub overwriting your HDD straight away.

It is worth making sure that grub boots up from a floppy disk before installing it in your HDD.

First, prepare a floppy disk which you can erase its contents.

Then, (as root if needed) do the following:

    # dd if=/usr/share/grub/i386-redhat/stage1 of=/dev/fd0 count=1      
    # dd if=/usr/share/grub/i386-redhat/stage2 of=/dev/fd0 seek=1 
   

Here, assume your root partition of Linux is /dev/hda3 and you have Windows installed in /dev/hda1 partition.

Let's reboot with the floppy disk in your floppy drive.

You will see

grub>

and your system waits for your command.

To start Linux do as below:

    grub> root (hd0,2)      
    grub> kernel /boot/vmlinuz-2.4.19-12m root=/dev/hda3      
    grub> initrd /boot/initrd-2.4.19-12m.img      
    grub> boot 
   

To start Windows:

     grub> root (hd0,0)      
     grub> makeactive      
     grub> chainloader +1      
     grub> boot 
   

grub> ker<TAB>

grub> kernel