Update: actually, after using it for a bit, it appears that XP runs at about the same speed in 5.0 as it did in 2.12.  It's just the initial boot that's very slow.  Does this message (which I discovered hiding under the QEMU window) have anything to do with it?

(qemu:27712): Gtk-WARNING **: Could not load a pixbuf from /org/gtk/libgtk/theme/Adwaita/assets/bullet-symbolic.svg.
This may indicate that pixbuf loaders or the mime database could not be found.


            - Michele