Win Web Hosting

Microsoft’s Vista Enterprise website explains how to obtain it:
http://www.microsoft.com/windows/products/windowsvista/enterprise/getit.mspx

Most important is the Volume Licensing Program you will need. Please see here:
http://www.microsoft.com/licensing/mla/

You can also contact a Volume Licensing Specialist:
http://www.microsoft.com/licensing/contact/default.mspx

In the United States, call (800) 426-9400, or visit the Microsoft Licensing Program Reseller page.

Hope this helps.