The problem investigated in issue8870 detected that bdist_wininst installers fail in Vista and Windows 7 with enabled UAC (user access control) when run from local drives with non-MS file systems and from network drives.

The error message returned in this case is not explanative at all.
"Failed to start elevated process (ShellExecute returned 5)"

Further investigation revealed that if network samba share requires authentication, and authentication passes, then the installer won't fail. Unfortunately, I can not setup network access to unauthenticated Samba shares right now to test behavior, but I attach installer generated with --user-access-control=force in case somebody can help.

The error message needs to be improved to give users immediate hint what Windows UAC doesn't allow to run privileged executables from non-MS file systems and/or network drives.