Default choice of operating system is turning on the computer, after the end of the basic input / output system - BIOS.Therefore, to change the operating system you need to reboot the computer to initiate - on Windows this is done from the main menu being opened by pressing the Win.After the start of a new cycle of loading and appears on the list of installed into the computer systems move through it line by using the arrow keys, and the selection is made by pressing Enter.This menu is displayed for 30 seconds (timer is also present on the screen), and then, if you do not make a choice, there is a loading OS default - it stands first in the list.
When you boot up your computer this menu does not appear, most likely it's disab
led in the settings.In this case, use the built-in operating system boot protocol control mechanisms.In Windows 7, this first press the key combination Win + Pause, then click the "Advanced System Settings" and "Advanced" tab of the new window, click "Settings" in the section "Startup and Recovery."
In the next open window with the settings put the check mark from the inscription "Display list of operating systems" and select the waiting time in seconds the user's choice.Then click OK in the two open windows and you can start to reboot to change the OS of choice.
Simultaneous operation of the two operating systems on one computer is not possible, but there are programs that are under the control of the main OS mimic the actions of another.If you install a "virtual machine", and will be able to switch between the primary OS and simulated without using the procedure for restarting the computer.Find software for implementing such a scheme may be the Internet - e.g., it may be VMware or Connectix Virtual PC.