Changing Ubuntu Natty 11.04 grub default booting operating system

Recently an acquaintance's computer needed significant repair. It had been used by several of his immediate family and some of them had downloaded significant amounts of dubious materials from dubious sources resulting in virus infection and system slowdown. I reinstalled a fresh copy of Windows XP + Ubuntu 11.04, dual booting, on the basis that both provided for his needs, namely office applications, email and internet. Ubuntu, as similar as its interface is to Windows from a basic perspective, was not to his taste, so I had to change the default boot order of Grub.