You don't need separate computers to run different operating systems. Sure, Windows is by far the most common OS running on the millions of PCs in daily use, but that doesn't mean you're stuck using just XP or Vista.
You can add a newer — or older — Windows version to your existing one, and you can choose which one to load from a boot menu when you power on the computer. The latest Macs also offer the ability to dual-boot Mac OS X and Windows via the company's Boot Camp utility. And both Macs and PCs can run popular versions of the GNU/Linux operating system, such as Ubuntu and openSuSE.
(Warning: Creating multiboot configurations often involves using disk-partitioning techniques that can damage or destroy your data. Before adding, removing, or resizing partitions, modifying boot loader software, or altering the master boot record, be sure to back up your files.)
Multibooting on Your PC
Q. I'm not sure I want to upgrade from Windows XP to Windows Vista. Can I just add Vista to my existing Windows XP installation so I can boot either one?
A. Yes. When you install Windows Vista, choose the Custom install option, and then install to a different partition than your existing Windows XP installation. To delete and create partitions, boot your system with the Vista install disc rather than running the installer within an earlier Windows version; this approach gives you additional options for creating and deleting (but not resizing) partitions. To shrink existing partitions and make room for a new one, use a third-party partitioning program like the free Partition Logic. After you install Windows Vista, the operating system's boot menu will give you the option of booting either Vista or your previous Windows version.
Q. How do I change which operating system boots by default, the delay before booting, and the menu text in the multiboot menus in Windows XP and Windows Vista?
A. In Windows XP, open the Control Panel's System applet, select the Advanced tab, and click Settings under Startup and Recovery. Select the default operating system from the drop-down list in the System Startup section, and select the delay time in the field next to 'Time to display list of operating systems'. Click Edit under System Startup to open the boot.ini configuration file in the Notepad text editor; this editor lets you modify the default text label (enclosed in double quotes) for each operating system in the menu. Windows Vista's boot menu options are nearly identical to those in Windows XP (click the Advanced system settings link in Control Panel's System applet, and then choose the Advanced tab), but Vista lacks the Edit button.
To modify the boot menu listings, open a Command Prompt window as Administrator (choose All Programs, Accessories, right-click Command Prompt, select Run as Administrator), and enter bcdedit. You'll see a list of the current boot menu settings, including separate sections for each operating system listed. To modify the menu text for a listed OS, use the command bcdedit /set identifier description "Menu text", where identifier is the identifier listed in the bcdedit output, and "Menu text" is the new menu text you want to create. For example, to change Windows Vista's default entry for Windows XP from the annoyingly vague 'Earlier Version of Windows' to the more specific 'Windows XP Home Edition', use the command bcdedit /set {ntldr} description "Windows XP Home Edition".
