Suppressing My Computer in File Open dialog box?

[Dan Kegel]

I'm creating a page of tips at
http://wiki.winehq.org/DisplayingUnixFilenames
for vendors shipping Windows apps on Linux with Wine
who want their apps to use Windows paths throughout
internally, but display Linux paths in the GUI

This is something I've been meaning to do ever since I helped port Picasa.
Picasa was an easy case, since it didn't use any standard widgets.
So now I'm wondering how to coax standard widgets into not leaking
Windows paths or naming conventions visually.

Does anyone know how to keep the Save File dialog box from
listing My Computer in the LookIn pulldown?  (I know how to
keep it from showing /, but I'd like to do the opposite, and
*only* show / and maybe the user's home directory, if possible.)