Backup Advice

I have customized my system setup a little & I'm looking for some advice on
how I should handle backups.

My computer itself has 2 hard drives. My C drive contains the operating
system, all programs & documents. The second D drive I have specified as a
'Media Drive' & this is where I store all of my digital photos & digital
videos. One of the features I like with vista is I am able to 'remap' the
default locations of 'Pictures', 'Video', etc so they are pointing to the
appropriate folders on my D drive.

I also have a 3rd NAS drive connected. The NAS drive is where my default
'music' folder is located. I use iTunes to rip/manage my music collection &
since 'Music' is mapped to the NAS drive, this is the location iTunes places
the iTunes folder (& associated library database files, etc). There is a
specific reason why my music folder is mapped in this way & the music is
stored on a NAS drive. I have a stereo component that streams my music to my
home multiroom audio system. Having everything music related on the nas
drive allows my music to be streamed, independent of my computer - doesn't
matter if my computer is on, in sleep mode, or even turned off my music is
still available since the NAS is always on.

My NAS drive is a 1TB drive & my music collection only uses ~100GB, so it
makes sense to use the NAS drive to save backups to as well. I have created
a separate 'backup' folder on the NAS & setup Vista backup to save backups to
this folder. The only problem I'm not sure how to handle backing up my
music. I have two concerns:
1. Since my music is already on the NAS drive, I shouldn't really be
creating a backup onto the same drive
2. Although I have check marked the box in Vista backup to include music
files, my music is not being backed up since it's not located on the C or D
drive.

So, my thoughts are... I should created a duplicate copy of my music
collection on my D drive & then allow Vista to do its scheduled backups which
would intern backup my music as well. But I have not figured out how to
create a duplicate copy of my music folder, other than manually
copying/pasting the folder off my NAS drive onto my D drive.

Having a duplicate copy of my music folder is something I would like to do
anyways - I have multiple copies of my digital photos as well (main location
on D drive, copy saved to DVD, backup on NAS) - DVDs make sense for photos &
videos, but my music collection is too big for DVDs.

Can anyone give any insite as to the best way of creating a duplicate copy
of my music folder. Feel free to give any advice as to a better way of
handling this as well.