Multibooting Windows 7

In today’s world of advanced OSs and low hard-disk prices, it certainly is not unusual for some users to experiment with different OSs. The world of consumer computing is ripe with many options. Along with just plain curiosity and experimentation, here are other good reasons to switch among or between OSs:

• Many users use two or more OSs because of application-compatibility issues. Hardware support issues occur, too: Windows 2000 and Windows XP might have drivers for older hardware that Windows 7 doesn’t support.

• Some users want to run specific applications or games in an optimal environment for their use.

• A developer might swap among Windows XP Professional, Windows Vista, and maybe even several different versions of Windows 7, to test application compatibility.

• Website developers need to use different OS versions to see how pages look and behave with corresponding web browser versions.

Other than buying multiple computers, there are two ways to accommodate such needs. You can multiboot (that is, select the desired OS at bootup) or you can run one OS in a “virtual” computer inside another OS (that is, in a special application program that lets the alternate OS think it’s running on a PC of its own). A “virtual” approach can be quite useful. Windows 7 uses a boot scheme introduced with Windows Vista based on so-called “Boot Configuration Data,” usually abbreviated as BCD. BCD is more complex than and incompatible with the boot scheme used in previous versions of Windows. While Windows 2000 and XP let you set up a boot menu from which you could select any version of Windows, as well as other OSs, Windows 7’s boot menu only lets you select Windows Vista or 7 versions, or “something else,” and all “something else” selections must be managed separately.

As a result of the boot manager changes, if you want to set up a computer that can boot several different versions of Windows and/or other OSs, you need to follow these guidelines:

• You must install each OS into a separate disk volume (drive letter). To get these separate volumes, you can create multiple partitions on one disk drive, or use multiple disk drives, or a combination of these two organizing principles.

• If you install multiple versions of Windows 7 on the same computer, the same rule applies: You must install each version in a separate disk volume. (If you do install multiple versions of Windows 7, see the “Editing Windows 7 Boot Menu Entries.)

• Install versions of Windows starting with the oldest and working toward the newest. For example, to set up a computer that can boot into Windows Me, Windows XP, and Windows 7, install Me first, then XP, then Windows 7.

• To install OSs other than Windows, such as Linux, you might need a boot manager that can recognize all the different OSs in use. Linux offers a choice of several different boot managers. Their use is beyond the scope of this book, but you should be able to find instructions on the Web for multibooting Linux and Windows 7.

To create a multiboot installation on a computer that already has Windows Vista installed, follow this procedure

1. Insert the Windows 7 DVD into your computer’s DVD-ROM drive. It should AutoPlay and present the Install Windows dialog box. If not, locate the setup.exe program in the Sources folder on the DVD, and double-click it. (Alternatively, you can restart your computer and boot from the DVD.)

2. To download, install, and use the Windows 7 Upgrade Advisor, as detailed previously, click the Check Compatibility Online link. Otherwise, to begin the in-place upgrade to Windows 7, click the Install Now link.

3. In the Get Important Updates for Installation dialog box, you are asked whether you want to download updates to the Windows 7 install files. Typically, for computers that have an active Internet connection, you are better off getting the updates. Make your selection by clicking it.

4. In the Please Read the License Terms dialog box, ensure that you read and understand the End User Licensing Agreement (EULA). When you’re ready, select the I Accept the License Terms option, and click Next to continue.

5. In the Type Your Product Key for Activation dialog box, you are asked to enter your Windows 7 product key. Enter the key and ensure that the Automatically Activate Windows When I’m Online option is checked, to enable Windows Product Activation. After entering the product key, click Next to continue.

6. In the Which Type of Installation Do You Want? dialog box, select Custom (Advanced) because here you’re performing a clean, multiboot installation of Windows 7, not an upgrade.

7. In the Where Do You Want to Install Windows? dialog box, select the partition into which you’ll install Windows 7. This must be a partition that does not already have a version of Windows installed on it. When you’re ready to proceed, click Next.

8. Follow the rest of the procedure described previously under “Typical Clean Setup Procedure,” from step 6 on through the end.

9. If you plan on installing another version of Windows 7 on this same computer, skip ahead to the“Editing Windows 7 Boot Menu Entries” section at the end of this chapter to rename the current version’s title in the boot menu.

10. You can check out the new Windows 7 boot menu, on the next restart of your computer.

The Skinny on Boot Scheme Changes
Here’s a rough sketch of what’s changed: In the boot scheme used by the Intel x86 versions of Windows 2000 and XP, the boot partition’s boot sector program loaded ntldr, which read the menu file boot.ini, and then loaded Windows. Aside from the boot sector, all of the stuff was in “super hidden” files (files marked with the system and hidden attributes), stored in the root directory. The Windows Vista and Windows 7 boot sectors load a file called bootmgr from the root directory, which loads a set of programs and DLLs in the \boot folder, which then reads the BCD file (actually a Registry hive), and then loads Windows. The BCD hive is also loaded into and visible in the Windows Registry after bootup. In a Windows 7 multiboot configuration, the root directory file bootsect.bak is a copy of the pre–Windows 7 boot sector (XP’s version of the boot sector).
Choosing “Legacy” from the Windows 7 boot menu loads and runs the original boot sector program, which carries on as before.

The reason for making this change was to create a common boot system that would work on both BIOS-based computers and computers using the newer EFI configuration system (built around Intel’s Extensible Firmware Interface). The impact of this new scheme is that the Windows 7 boot menu can offer only Windows 7, Windows Vista, and Windows Server 2008 versions, where anything using the older boot loader gets lumped under the “Legacy” entry. The boot.ini file is used only to list and load non-BCD operating systems.

Source of Information : QUE Microsoft Windows in Depth

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