File overwrite problem in cab file on 5.0

[Nick1394]

hey, guys
I have a Dell X51, which is WM5.0.
And I have built my cab file with CABWIZ.EXE. I have one file, I don't want it to be overwritten if the file is already there.
So I use flag COPYFLG_NO_OVERWRITE 0x00000010, but, it works for all my old handhelds. It does not work on WM5.0, the dell x51.
I also tried to make the cab file in vs2005, but I can not find any place to set the file copy options.
Does anyone know how to do this on 5.0?