How to create a file in "Public" on vista OS?

hello.
I use following code to create a file in my programe
CFileException Error;
CFile oFile;
UINT nFlags = CFile::modeCreate | CFile::modeWrite;
try
{
if (oFile.Open(oPath, nFlags,Error))
{
oFile.Close();
}
}
catch (CException * pEx)
{
pEx->ReportError();
pEx->Delete();
}
the function of oFile.Open return false.
but in other folder (not in Public folder) is Okay

thanks!