[Snuffy]

http://www.windowsmarketplace.com/co...Id=395&tabid=1

detailed instruction on what to do and what not to do.
samples:

Upgrading to Windows Vista
Note: Windows Vista does not support Serial Key devices. If you are upgrading and you currently use Serial Keys with an alternative input device, you must turn off Serial Keys and install another input option before the upgrade. To turn off Serial Keys in Windows XP, open Accessibility Options in Control Panel. On the General tab, under Serial Key devices, clear the Use Serial Keys check box. For more information, go to the Microsoft Accessibility website.

Please note: The Windows Vista Upgrade Advisor works with 32-bit editions of Windows XP and Windows Vista, except Windows Vista Enterprise. It will not work with other versions of Windows including Windows 2000 and Windows 98. The Windows Vista Upgrade Advisor does not collect or send any personal, identifiable data to Microsoft Corporation or third parties. See the Upgrade Advisor privacy statement for details.

4. Update your anti-virus program (if necessary), run it, and then disable it.

5. Can I upgrade to a 64-bit edition of Windows Vista if I update my machine to a 64-bit processor down the line?
Yes, if your machine has a 64-bit processor and is capable of running the 64-bit edition of Windows Vista, you can upgrade to the 64-bit edition of the Windows Vista product that you purchased, in accordance with the license terms of your product. Remember: you need to be running a 64-bit Windows operating system to install your 64-bit Windows Vista edition. You can do that if you have a 64-bit Windows Vista DVD (For the price of shipping and handling you are entitled to a Windows Vista DVD with your Windows Marketplace purchase. See below for more information). Also, in accordance with the transfer rights contained within the license you purchased, you can transfer this upgrade to a different PC, installing either the 32-bit or 64-bit edition on that PC. Please refer to the Microsoft Software License Terms of the product license to determine the terms for either of these options.

10. I’m having problems with installing Windows Vista. Who can I contact?
If you have any questions during your Windows Vista upgrade installation, please contact the Windows Vista Support Team. Support for Windows Vista can be found at http://www.support.microsoft.com or you can call Support Customer Care: 1-800-MICROSOFT (U.S. and Canada only).

PLEASE READ these very informative Instructions. If your having problems with upgrades or simply installing Vista...