Change the boot order
From MEPIS Documentation Wiki
Open the /boot/grub/menu.lst file as root (type "kdesu kwrite /boot/grub/menu.lst" in run command or terminal) and add the following option:
default n
where "n" should be 0 to boot the first entry in the menu, 1 for the second and so on.
Another way is to just reverse the order of entries (don't apply both methods since they will cancel each other).

