2008 DC containing FSMO roles in a 2003 function domain

[billycat]

Any one have any idea if this is supported? Upgrading DCs and would like to go straight to 2008 x64, but am unsure whether or not this would be wise considering id be using one of these 2008 as the FSMO role holders.

 

[TechyMcSe2k]

Upgrading Active Directory Domains to Windows Server 2008 AD DS Domains

http://technet.microsoft.com/en-us/library/cc731188.aspx

Here is a good start.