Windows 7 and Vista users who want to dual-boot their operating systems should know how to set the default operating system. By default, Windows 7 installs on the C: drive and Windows Vista installs on the D: drive. Dual-booting means that you can use both operating systems at the same time. To set the default OS in a Windows 7 or Vista dual-boot setup, follow these steps:

  1. Open Start menu and select “Control Panel.”
  2. Double-click “System.”
  3. Under “System Properties,” click on “Default System Settings.” In the “Default System Setting” window, under “Operating System,” click on “Windows 7 (or Vista).” If you are dual-booting with Windows XP, then under “Operating System” click on “Windows XP (or earlier).”
  4. In the next window, under “Advanced Options,” make sure that the check box next to “Install Windows Automatically (when computer starts)” is checked. Click OK to save your changes and close the window.
  5. Restart your computer and wait for it to boot into Windows 7 or Vista as normal. When it does, you will be prompted to choose which OS you would like to use as your default OS. ..

First, you’ll need to right click on Computer and select Properties:

Next, click Advanced System Settings

Now click on the Settings button under Startup and Recovery

And just select the operating system you want to use:

Easy stuff. You could also use the bcdedit command to do the same thing from the command line, but it’s probably easier this way.