You can have multiple operating systems on a single computer. Some software applications may require the most recent version of an OS, while other applications require an older version. There is a dual-boot process for multiple operating systems on a computer. During the boot process, if the Windows Boot Manager (BOOTMGR) determines that more than one OS is present, you are prompted to choose the OS that you want to load, as shown in Figure 1.

To create a dual-boot system in Microsoft Windows, the hard drive must contain more than one partition.

The oldest OS should be installed on the primary partition or the hard drive marked as the active partition first. Install the second OS on the second partition or hard drive. The boot files are automatically installed in the active partition.


During the installation, the BOOTMGR file is created on the active partition to allow selecting the OS to boot on startup. You can edit the BOOTMGR file to change the order of the operating systems. You can also change the length of time allowed during the boot phase to select the OS. Typically, the default time is 30 seconds. This time period delays the boot time of the computer by the specified time, unless the user intervenes to select a particular OS. If the disk has only one OS, change the time to 5 or 10 seconds to boot up the computer faster.

NOTE: In Windows XP, the BOOT.INI file fills the role of the BOOTMGR file.

To change the time to display the operating systems, use the following path:

Select Start > Control Panel > System and Security > System > Advanced System Settings > click the Advanced tab > In the Startup and Recovery area, select Settings

To edit general boot configuration data in Windows 7 and Vista, use the bcdedit.exe command-line tool, as shown in Figure 2. To access the bcdedit.exe tool, use the following path:

Select Start > All Programs > Accessories > right-click Command Prompt > Run as administrator > Continue > type bcdedit.exe

To edit the boot.ini file in Windows XP, use the following path:

Select Start > right-click My Computer > Properties > Advanced tab > in the Startup and Recovery area, select Settings > click Edit