Most computers come with an operating system, but you can install multiple operating systems on a single computer. Install both operating systems and choose between them at startup.
Google and Microsoft have discontinued Intel's dual-boot Windows and Android PC plans, but you can install Windows 7 at the same time as Windows 8.1, Linux and Windows on the same computer, and Windows or Linux at the same time as Mac OS X.
How dual system booting works
A computer's operating system is usually installed on its internal hard drive. When you boot up your computer, the BIOS loads the bootloader from the hard drive, and the bootloader boots the installed operating system.
There is no limit to the number of operating systems you can install, you can put a second hard drive in your computer and install the operating system in it, selecting the hard drive you want to boot in the BIOS or boot menu. You can also boot the operating system from external storage media, such as a real-time Linux system or a Windows To Go USB drive.
Even if you only have one hard drive, you can install multiple operating systems on this hard drive. By dividing a drive into a number of different partitions, you can provide one partition for one operating system and another partition for another operating system and split the drive between them. (In fact, many operating systems use multiple partitions.) The point is that you use one part of the drive for one operating system and another part of the drive for another. ）
When you install a Linux distribution, it usually installs the Grub bootloader. If Windows is already installed, Grub loads at boot time, rather than the Windows bootloader, allowing you to choose which operating system to boot. Windows also has its own bootloader, which you can use to choose between different versions of Windows if you have more than one version of Windows installed.
Why dual systems
Different operating systems have different uses and benefits. Installing multiple operating systems allows you to quickly switch between the two operating systems and have the best tools for the job. It also makes it easier to try and experiment with different operating systems.
For example, you can install Linux and Windows at the same time, use Linux for development work, and boot into Windows when you need to use Windows-only software or play PC games. If you like Windows 7 but want to try out Windows 8.1, you can install Windows 8.1 with Windows 7 and choose between the two at startup knowing you can always go back to Windows 7. If you're using a Mac, you can install Windows with Mac OS X and launch it whenever you need to run Windows-only software.
Instead of setting up a dual-boot system, you can use virtual machine software, but a dual-boot system allows you to use both operating systems at full local speeds on your hardware. You don't have to deal with the overhead of virtual machines, which is especially bad when it comes to 3D graphics. The disadvantage is that you can only use one installed operating system at a time.
Switch between operating systems
If each operating system is installed on a separate drive, then you can switch between the two by selecting a different drive as the boot device each time you boot up, but this is inconvenient, and you may have two operating systems installed on the same drive, so that's where Boot Manager comes in.
Switch between installed operating systems by restarting your computer and selecting the installed operating system you want to use. If you have more than one operating system installed, you should see a menu when you start up your computer. This menu is usually set when you install a different operating system on your computer, so you won't see if you're only installing Windows or Linux.
Set up a dual-boot system
Setting up a dual-boot system is fairly easy. Here's a quick overview of what to expect:
Windows and Linux: If you don't have an operating system installed on your computer, install Windows first. Create a Linux installation media, boot into the Linux installer, and select the option to install Linux with Windows.
Windows & Another Windows: Shrink the current Windows partition from inside Windows and create a new partition for other versions of Windows. Boot into a different Windows installer and select the partition you created.
Linux and another Linux: You should be able to dual-boot both Linux distributions by installing one first and then the other. Choose to install the new Linux system with the old one. Resize the old Linux partition in the installer, and if the installer doesn't do it automatically, create a new partition to make space.
Mac OS X 和Windows: Mac OS X 附带的Boot Camp实用程序允许你 在Mac 上轻 松设 置Windows双启动 系 统。
Mac OS X and Linux: Boot Camp doesn't allow you to set up a dual-boot Linux system, so you'll need to do more work here.