Usually Ubuntu is set to be the default, i.e. the one that will be
loaded if nothing is done during the time-out. There's a tool you can
install called Grub Customizer that allows graphical control over all
the parameters - link below:

http://ubuntuforums.org/showthread.php?t=1664134

This should address any Grub configuration issues :-)

BM> Can someone tell me the steps to changing the default from Windows
BM> Vista to Ubuntu 12.10.