You will need
  • A computer with two operating systems.
After you installed the second operating system, turn on the computer. During boot the system should have a dialog box which will list the operating systems that are installed on your computer's hard drive.
Use the arrows on the keyboard to select the operating system you want in the moment, and press Enter. Then your chosen OS will boot as normal.
If a dialog box in which to select the operating system, did not appear, and simply booted one OS, you have to enter some settings. Just right-click on the icon "My computer" and from the context menu select "Properties". In the next window click on "advanced system settings".
Then in the Advanced tab, find the section called "startup and recovery" and select "Settings". Locate the "Display list of operating systems" and select it. After that, click OK. In the next window, also click OK.
Then restart the computer. Now a dialog box in which you can select your operating system, you will get exactly.
If you have the computer has two hard drives, and each OS is installed, the selection window of the operating system may not appear. In this case, to select the OS by selecting the hard disk where you installed the desired operating system.
Turn on the computer and immediately after that, repeatedly press the Del key. So you get into the BIOS of the computer. Now use the arrows on the keyboard to select the boot device priority. In this section the number "1" put the hard disk with the right at the moment the operating system. Save the settings. The computer will reboot and will start with your chosen hard drive with the desired OS.