Upgrade Windows XP License to Vista

Hello ,to All

I Have A Windows Xp Oem purchased 3 Year Back , Installed in my dell system, i Was Recently Thinking of Upgrading it To Windows Vista , But i did Not Whether my xp License Would Work With Vista or DO i Have to Purchase a new License for Windows Vista , The Reason i am asking this because Whenever i have purchased any software , I Have Alway got an Free uogradation offer for lifetime for particular product , But i dont Know About This in Windows Vista , Please Help
Thank you in advance

Hello , I Think you Can Upgrade for Free to Windows Vista , and Not Only Upgrade You Can Also Downgrade From Windows Vista to Windows xp , if You Dont like it , as Stated In this Page From microsoft

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The future of Windows XP

The future is here and it's better than ever. Windows Vista is Microsoft's latest operating system with proven benefits over past versions of Windows. Better security, improved productivity—and that's just the beginning.

Maybe you're one of the people who haven't tried Windows Vista yet. See the experience in action with the Mojave Experiment where we exposed users to a whole new experience. Studies prove that people love what Windows Vista has to offer, so why not upgrade and see the benefits of Windows Vista today?

An overwhelming majority of Windows Vista customers like it better than their last operating system. Perhaps that's why more than 140 million copies of Windows Vista have already sold, making it the fastest selling operating system in Microsoft history.

Move to Windows Vista with confidence today. The Windows Vista Compatibility Center and the Windows Vista Upgrade Advisor can help you determine whether your hardware and applications are compatible and help you find solutions to problems you might encounter.

We know you love Windows XP and you’re in good company. Hundreds of millions of Windows XP users are fans of the operating system, and many depend on Windows XP to run legacy applications and hardware not yet compatible with Windows Vista. Even though we’re retiring Windows XP, we won’t leave you hanging. Our Microsoft Support Lifecycle explains it all.

You can still buy new PCs and use Windows XP. Windows Vista Business and Windows Vista Ultimate have downgrade rights that let you return your operating system to Windows XP. We plan to provide support for Windows XP until 2014.

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If you choose to purchase an upgrade version of Windows Vista to upgrade XP, you will no longer be able to use that version of XP. Either on another system, or as a dual-boot option. The key will be invalidated, preventing activation.

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13. UPGRADES. To use upgrade software, you must first be licensed for the software that is eligiblefor the upgrade. Upon upgrade, this agreement takes the place of the agreement for the software you upgraded from. After you upgrade, you may no longer use the software you upgraded from.

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If you are currently using Windows 2000 Professional or Windows XP Professional x64, you are eligible for an upgrade copy to a corresponding or better edition of Windows Vista, but a clean install is required.

Upgrade copies are not available for versions of Windows earlier than Windows 2000. These earlier versions of Windows require you to install a full copy of Windows Vista.

If the edition of Windows Vista that you choose to install will result in a loss of functionality over your current edition of Windows, you will need to do a clean install, or install Windows Vista to a new partition on your PC.