Dual-Booting Win XP and Vista

Just when you have Windows XP working exactly the way you want, along comes Windows Vista. You want the new OS, but you need to keep the old one as well. Do you need to buy a new PC?
No way: Dual-boot instead.

Dual-booting means installing two operating systems on your computer and, at start-up, choosing which one to launch. Each OS runs independently of the other, with its own settings and its own installed programs. You can install two or more instances of Microsoft Windows XP or of Vista, or any combination of Win XP, Vista, Linux, and older Windows versions. But right now, I'll focus on how to add Vista to your existing Win XP system.

Before starting, you need either a separate partition on your hard drive or a separate drive; if you install Vista on the partition where Windows XP is already installed, Win XP will no longer run. Open My Computer, and make sure it shows multiple hard drive icons (one for each partition). Now check whether the second partition has enough space for Vista (at least 20GB to 30GB if you plan to install major programs). If not, or if you don't have a second partition, start with step 1 to create one. Everyone else can skip right to step 2.

2 Install Vista
At this point, you install Vista, either from within Win XP by inserting the Vista disc and letting Autorun do its thing, or by inserting the disc and rebooting the system (as long as your PC is configured to read the optical drive before the hard drive).

Choose Installation Type
You have two main tasks during the installation. First, on the "Which type of installation do you want?" screen, choose Custom; selecting Upgrade changes your Win XP installation into Vista, which of course won't result in a dual-boot environment. Then, on the subsequent screen, you have to tell Vista where you want it installed; this is where you choose the new partition.

Start It Up
After that, just wait for the installation to finish. Your PC will reboot itself more than once, and with each reboot you'll see your new Boot menu, with Earlier Version of Windows at the top and Microsoft Windows Vista—highlighted—next. Use the arrow keys to select the OS you want to load, and press Enter. — next: Step Three: System Check

3 System Check
The installation process warns you if you select a partition on which you already have Windows installed. If that happens, click Cancel and choose the correct partition. — next: Step Four: Tweak It

4 Tweak It
Once Vista is installed, you can configure the Boot menu. But where earlier versions of Windows conveniently used the boot.ini file to store boot details, Vista uses the Boot Configuration Data (BCD) store—bcdedit.exe from the command prompt—and this utility is stunningly unintuitive. You're better off downloading VistaBootPro (www.vistabootpro.org) or EasyBCD (www.neosmart.net), both of which give you a GUI environment to work with. — next: Finally, Two Warnings

Finally, Two Warnings
1 The BCD provides a more robust start-up environment for Windows, but the downside is that if you want a multiboot system, you must be sure to install Vista last. If you put Vista on a machine and install Windows XP afterward, Vista won't start, because Boot.ini, which Win XP adds automatically, will render the BCD useless (although you can recover it by running the fixntfs.exe utility from within Win XP).

2 Even when your Win XP/Vista machine is happily dual-booting, one problem remains. As you work in Vista, the System Restore utility automatically creates restore points—and you can create them yourself—that let you launch the system in a previous state and recover from errors. But when you exit Vista and launch Win XP, the older OS deletes the Vista restore points.