Boot a live Linux CD, mount the XFS volume read-only, mount the Windows drive (ntfs-3g) R/W, and copy your files over.
Okay, so I rummaged through my pile of boxes, finally found a DVD burner, and made an Ubuntu live disc and booted to it. I didn't need to mount the existing drives because they came up automatically, and I was easily able to mount the NAS drive with no troubles whatsoever. I copied all the data off and now I'll wipe the drive for use as a regular NTFS disc.
Thanks for the help, folks. I'm still interested in trying out the Ubuntu VM, so I'll play around with that.