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Boot Dual Vista and XP
http://www.vistaarticles.com/articles/471/1/Boot-Dual-Vista-and-XP
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Published on 11/13/2007
 
Learn how to dual boot Windows Vista and Windows XP.

Boot Dual Vista and XP

If Vista is already Installed:

1. Install XP in different partition.
2. Using Vista DVD repair the installation of Vista Boot Manager.
3. Login to Vista and run the following commands via command prompt:

bcdedit /create {ntldr} /d "Windows XP"
bcdedit /set {ntldr} device boot
bcdedit /set {ntldr} path \ntldr
bcdedit /displayorder {ntldr} /addlast

4. Restart.

You can now choose OS using the boot menu.

If XP is already Installed:

Simple. Choose custom install while installing Vista in different partition. Boot menu will automatically be created.