I found this online:
http://cyberjunction.wordpress.com/2007/06/25/vista-downgrade-rights/How to downgrade Vista Business/Ultimate to XP Pro (Who will do this anyway? Well, if you have custom applications that only run on XP Pro, you have no choice or use Virtual PC). Follow the step by step guide below.
1.
Install the Machine with XP PRO Media and get any valid XP Product Key.
2.
After finishing the installation, there will be 2 options for you to pick for the Windows Activation. Activate online or activate through Phone Call. Pick activate through Phone Call.
3.
The system will show a series of Installation ID for activation.
4.
Send an email to
[email protected], and include all the information below:
1.
XP PRO Product Key and COA (Certificate of Authenticity) installed to the machine
2.
Vista Business/Ultimate Product Key and COA if possible
3.
XP Installation ID that shown in the system
4.
Customer information
5.
Microsoft will verify the information and respond within 24 hours. (Common case is about 5-6 hours)
6.
You will received an email from SEAPA, with the activation key. Key in the activation key.
You have 30 days to activate your Windows.