Thanks for the link, Greg2
Unfortunately the KDE4 folder widget, when pointed to the common partition, covers about a quarter of the desktop, and even worse, reveals the contents of the common partition - something I certainly do not want to be dislayed.
I put an icon for the Dophin file manager on the desktop as a workaround. That may be as close as it can to an icon for the common partition, being a bit like in Gnome and KDE 3. Pity it doesn't seem to work in KDE4. I sometimes wonder why simple things are encomplicated for no obvious reason. Maybe I should switch back to KDE3...
Thanks,
Helmut