pidlRoot
A pointer to an item identifier list (PIDL) specifying the location of the root folder from which to start browsing. Only the specified folder and any subfolders that are beneath it in the namespace hierarchy will appear in the dialog box. This member can be NULL; in that case, the namespace root (the desktop folder) is used.

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///  callbak for folder_browser
INT CALLBACK BrowsePathProc(HWND hwnd, UINT uMsg, LPARAM lp, LPARAM pData) 
{    TCHAR    szDir[MAX_PATH];
    static HWND hTitle;
    switch(uMsg)
    {
    case BFFM_INITIALIZED:
            if(((TCHAR*)pData)[strlen((char*)pData)-1]=='\\')
                _tcsrchr((TCHAR*)pData,'\\')[0]=0;
            SendMessage(hwnd, BFFM_SETSELECTION, TRUE, pData);
        break;
    case BFFM_SELCHANGED:
        if (SHGetPathFromIDList((LPITEMIDLIST) lp ,szDir))
        {
            SendMessage(hwnd,BFFM_SETSTATUSTEXT,0,(LPARAM)szDir);
        }
        break;
    }
    return 0;
}

BOOL BrowseForFolder(TCHAR *pszPath, HWND hWnd, TCHAR *pszTitle)
{
    BROWSEINFO bi;
    LPITEMIDLIST pil;
    bi.hwndOwner = hWnd;
    bi.pidlRoot = NULL;
    bi.pszDisplayName = pszPath;
    bi.lpszTitle = pszTitle;
    bi.ulFlags = BIF_RETURNONLYFSDIRS;
    bi.lpfn = BrowsePathProc;
    bi.iImage = 0;
    bi.lParam = (long)pszPath;
    pil = SHBrowseForFolder(&bi);
    if(pil)
    {
        SHGetPathFromIDList(pil, pszPath);
        return TRUE;
    }
    return FALSE;
}

int CALLBACK Browse4FolderInitPathProc(HWND hwnd, UINT uMsg, LPARAM lParam, LPARAM lpData)
{
    if (uMsg == BFFM_INITIALIZED) {
        LPCTSTR pszInitialPath = reinterpret_cast< LPCTSTR >(lpData);
        ::SendMessage(hwnd, BFFM_SETSELECTION, TRUE, reinterpret_cast< LPARAM >(pszInitialPath));
    }
    return 0;
}

//...
BROWSEINFO bi;
bi.lpfn = &Browse4FolderInitPathProc;
bi.lParam = "C:\\MyFolder";
::SHBrowseForFolder(&bi);

CEM>BOOL BrowseForFolder(TCHAR *pszPath, HWND hWnd, TCHAR *pszTitle)
CEM>{
...
CEM>    pil = SHBrowseForFolder(&bi);
CEM>    if(pil)
CEM>    {
CEM>        SHGetPathFromIDList(pil, pszPath);
CEM>        return TRUE;
CEM>    }
CEM>    return FALSE;
CEM>}

CEM>

SHBrowseForFolder
...
It is the responsibility of the calling application to call CoTaskMemFree to free the IDList returned by SHBrowseForFolder when it is no longer needed.