In the XMMS Load Files dialog box, there should be "Add selected files" and "Add all files in directory" buttons. You should be able to hold <CTRL> and select multiple files then click "Add selected files". Also, in the text selection box, you can do stuff like "*.mp3<TAB>" and the file list should refresh to show only .mp3 files.
To find out where hdb1 and hdb3 are mounted, right-click the desktop icons and choose properties. It should tell you where it's located (in Gnome, for my music, the properties window shows "Location: /mnt" and "Name: music", so I can find the files in XMMS by changing to /mnt/music). You can also open a terminal and run mount
, it'll show something like this
[mascmdan@odin proc][ :) ]# mount
/dev/hda8 on /mnt/music type xfs (rw)
I don't know about the surround sound, though