You have one hard drive? You can make the XP the primary and active, create an extended partition with 1 logical partition occupying the entire extended partition and install Vista RC1 into that logical partition. That way when you boot Vista up, XP pro becomes drive D and you can view it's content. The dual boot part Vista will automatically handle that for you, you don't really need to do anything except make a partition and install Vista through the DVD.
If you have SATA hard drive it should be supported automatically.