Odds 'n' ends: Q's re Gnome+KDE, ark, and Gnome's CD player

Not really Knoppix-specific, but some general questions:

Gnome 2.6 seems to use the same ~/Desktop file that KDE does. I mostly use KDE, but it's still annoying to log into Gnome and see a bunch of unuseable icons from KDE on the desktop (and if you delete them, they go away in KDE, too). Is there a way to tell Gnome to use another desktop folder, rather than simply creating a new user account just for Gnome?

When opening a *.tar.gz (or *.tgz) archive, ark keeps throwing up the error message "The utility is not in your PATH. Please install it or contact your system administrator." But gzip and gunzip are definitely in my PATH. I get the same error when creating one, even though it does create it. What's going on? (The error message seems to be about gz, not tar.)

Finally, I'm not getting any sound out of Gnome's CD player (although system sounds in Gnome and KDE work, as well as sound from xmms -- playing CDs too, xine, etc.) -- what's going on there?

Thanks for any help.