Dual Booting

I have a computer with Windows and Ubuntu and every time you start the computer you choose whic OS you want. But my parents that don't know anything about computers need to use it because our other computer broke. I want to select Windows to bbot every time I start then when I want to use the computer when I click the on button I can click a button to choose ubuntu. This will be easier for my parents to not go all the way down the list and select windows every time it starts.