Estou alterando os ícones de pasta com a função c #. Está funcionando bem, mas o problema está funcionando pela primeira vez. Quero dizer, não consigo alterar o ícone da pasta para a qual já mudei o ícone. Aqui está o código abaixo:

static void Main(string[] args)
{
    LPSHFOLDERCUSTOMSETTINGS FolderSettings = new LPSHFOLDERCUSTOMSETTINGS();
    FolderSettings.dwMask = 0x10;
    FolderSettings.pszIconFile = @"C:\Program Files (x86)\Common Files\TortoiseOverlays\icons\XPStyle\ModifiedIcon.ico";
    FolderSettings.iIconIndex = 0;

    UInt32 FCS_READ = 0x00000001;
    UInt32 FCS_FORCEWRITE = 0x00000002;
    UInt32 FCS_WRITE = FCS_READ | FCS_FORCEWRITE;

    string pszPath = @"D:\Downloaded Data";
    UInt32 HRESULT = SHGetSetFolderCustomSettings(ref FolderSettings, pszPath, FCS_WRITE);
    //Console.WriteLine(HRESULT.ToString("x"));
    //Console.ReadLine();

}

[DllImport("Shell32.dll", CharSet = CharSet.Auto)]
static extern UInt32 SHGetSetFolderCustomSettings(ref LPSHFOLDERCUSTOMSETTINGS pfcs, string pszPath, UInt32 dwReadWrite);

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
struct LPSHFOLDERCUSTOMSETTINGS
{
    public UInt32 dwSize;
    public UInt32 dwMask;
    public IntPtr pvid;
    public string pszWebViewTemplate;
    public UInt32 cchWebViewTemplate;
    public string pszWebViewTemplateVersion;
    public string pszInfoTip;
    public UInt32 cchInfoTip;
    public IntPtr pclsid;
    public UInt32 dwFlags;
    public string pszIconFile;
    public UInt32 cchIconFile;
    public int iIconIndex;
    public string pszLogo;
    public UInt32 cchLogo;
}

Qual seria a razão