Back them up in case you have issues develop. You should not have any
problems but there are some kb articles about various media files not
reading right after an upgrade. Not a common problem, but plan accordingly.
No. There is no difference between upgrading an OEM XP to Vista and
upgrading a retail XP to Vista other than the possibility of proprietary
drivers in the case of the OEM version. But that would have nothing to do
with mp3 files. Obviously an upgrade from XP to an OEM Vista is not
possible.