Alas, the installation and activation instructions appear to not be
applicable to Ubuntu 11.10, which doesn't have the range of choices in
System > Preferences > Appearance that earlier versions did. I don't
know yet whether the function is hidden somewhere else, or if one
needs to install the Gnome Tweak Tool, or what one can do. I only
discovered this today and haven't seriously started researching the
matter.
Meanwhile, however, I've discovered that the Radiance theme in Ubuntu
11.10 looks very much like the "XP-Silver" theme except that
highlighting is orange (menu items, checkboxes, default pushbuttons,
etc) and the drop-down list boxes are as Hazel described. My (possibly
faulty) memory of the earlier version of the Radiance theme is that it
didn't have enough contrast, but on one of my laptops at least, the
contrast now looks fine. However, it looks a bit less like Windows or
Mac.
--Jean