How To: Add Windows XP to Your Vista System

What you need:
1. Windows XP Installer CD
2. Vista DVD disc

First things first, back up your system or any important files you can't afford to lose. If you're ready to go follow these steps:

1. In Vista, click Start, type diskmgmt.msc, and press Enter. Click Continue if prompted by User Account Control.

2. Right-click a drive and choose Shrink Volume. Specify the amount to shrink, which in this case is the amount you want for your XP partition. If you want to allot 10GB of hard disk space for your XP system, type in 10000 in the box. Click Shrink.

3. Right-click the newly available area and choose New Simple Volume. When prompted, check Perform a quick format to format the volume with NTFS.

4. When the wizard is done formatting the new volume, you can assign or rearrange drive letters as needed.

To do that, right-click a volume or the CD/DVD drive and choose Change Drive Letters and Paths. If a volume hasn't got a drive letter yet, click Add. Otherwise, select the drive icon in the dialog box and click Change.

5. When you're done with partitioning, exit Disk Management. Insert your XP disc into the drive and restart your system. Boot from your XP CD.

6. Install XP. When asked for the target drive, select your new partition and press Enter. When prompted choose Leave the current file system intact (no changes) and press Enter. Continue the installation process until it's finished and XP has started.

7. Your system now boots to XP, so we'll need to do some fixing to set up a boot menu. Insert your Vista DVD and restart the computer from it. Click Next in the first screen.

8. Don't click Install when prompted! Instead, click Repair Your Computer in the lower-left corner.

9. When the System Recovery Options dialog appears, make sure Microsoft Windows Vista is selected and click Next. In the next dialog box, select the Command Prompt option at the bottom.

10. In the command-prompt window, type the following commands and press Enter after each one:

bootrec.exe /fixMBR
bootrec.exe /fixBoot

11. Close the command prompt and click Restart.

12. When your computer has booted into Vista, click Start, type cmd.exe, and press Ctrl+Shift+Enter to make the command window open with elevated privileges. Click Continue, if prompted by User Account Control.

13. Type the following commands in the command window, one at at time, pressing Enter after each one. After each command, you should get the response, "The operation completed successfully." A response of, "The specified entry already exists," is OK, too. If not, retype your command to make sure you've entered it correctly. If Vista is installed on a drive other than c:, change the first command below to use the proper drive letter. The curly braces around {ntldr} in each command must be typed exactly as shown:

bcdedit -set {ntldr} device partition=C:
bcdedit -set {ntldr} path \ntldr
bcdedit -displayorder {ntldr} -addlast
bcdedit -set {ntldr} description "Microsoft Windows XP"

The next time you restart your system, you should be see a prompt that will let you choose between Vista or XP. Select the one you want and press Enter.