Changing the default operating system of dual-boot

First, a little picture of where to look for the spot to do all this....

Go to Control Panel > System, and in the left margin, click Advanced System Settings, and on its Advanced tab, look down for Startup and Recovery. In it,
go to and click on Settings. The default operating system is shown in the little
box, and there is a small black arrowhead at its right-hand end. Click that to open the drop-down showing other choices. Click on the one you want to use,
and it becomes the default. You can also change the time allowed for displaying the list of operating systems during a startup, by changing the number of seconds shown in the little box under the default setting line.

And here's what it looks like in a boot manager program when you're done.