Have you installed Ubuntu Linux alongside Windows? If yes, then you’d end up with a boot manager with Ubuntu Linux as the default operating system to start. But if you want to automatically start Windows instead (or any other operating system) then you’ll have to download “Startup manager“.
Install it from the terminal:
sudo apt-get install startupmanager
How to use the Startup manager?
1. Go to System > Administration > StartUp-manager
In the opening window, you’ll see Boot options tab. Just click on Default operating system option and choose the operating system you want to load as default at computer startup. You can further customize by changing the boot delay too.
2. Click on “Close” button, and let the program do its magic. Restart to make the changes take effect.