Your XP won't boot on your new hardware. If it came pre-installed on the old hardware it'll have an OEM serial number tying it permanently to the old hardware, and MS will not validate it on new hardware even were you to repair-install it.
However, all of the data on the HDD should be accessible to Vista without you needing to do anything.
You should be able to open your libraries of music and photos from the old HDD via Explorer or with your chosen apps exactly as if they were on the new HDD.