This is fairly a simple task.
First, on your grub screen, locate the entry that you want to setup as the default choice. In my case, it was my Maverick install, located at 7 from the top.
Next, open the /boot/grub/grub.cfg,
ikhsan@Mach5-NX:/$ sudo nano /boot/grub/grub.cfg
Find the line that says set default=”0″ , change it to set default=”7″ or whatever the correct number on your system is
### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="7"
…and then reboot.