You would contact Dell. You will have an OEM verison of windows and Microsoft will not support you. Your support will be provided by Dell or Here on the forums. Don't hesitate to post questions here as there is a vast wealth of knowledge and support to be found here. Just remember this is a user to user forum. 
Does anyone know if the Windows Vista Ultimate (Product) Red Service Pack 1 that comes with the XPS One (Product) Red is able to upgrade to 64 bit? After talking with some advisors on the Dell Chat feature they told me that even though the system comes with Vista Ultimate, the system will only come with a 32 bit OS installed.  I checked the Microsoft website and it says that you can upgrade any Vista 32 bit product to the 64 bit by getting some CD but it also says that "Note: 64-bit media is included in the box with Windows Vista Ultimate" ([URL] bottom of page). From the specs on the website, it looks like the system should be able to handle a 64 Bit OS. Can anyone clarify this?
Windows Vista Ultimate (64 bit?) on XPS One (Product) Red