how to custom-draw an item in windows desktop window with win32 sdk

Question

I have a file in windows desktop window. I want to custom-draw it instead of the normal icon and text. I almost implement it via the following steps, 1. make a dll in which the IExtractIcon interface is implemented, then register a icon handler shell extension for the file to make the dll loaded by explorer.exe. 2. in the dllmain function of the dll, subclass the desktop window to make custom-drawing.

This almost worked, but still have some problems: 1. In winxp, the dll loaded only once. after restart the PC, the dll wouldn't be loaded, except I maked another file with the same extension. I guess the reason is the desktop has cached the icon so it doesn't need to load the dll to extract icons. But why win7 works. What can i do to make the system always load the dll?

1. The file always have an extension in file system, but when it is displayed in desktop, the extension might not be displayed. How can I get the full name of the file according to the desktop list-view item?

or is there any other way to make the explorer.exe load my dll automatically?

here is the IExtractIcon code:

HRESULT CShellIcon::GetIconLocation(UINT uFlags, LPWSTR szIconFile, UINT cchMax, LPINT piIndex, UINT* pwFlags)
{ 
    // I inject the dll to subclass the desktop window
    SubclassDesktop();

    *piIndex = 0; 

    *pwFlags = GIL_DONTCACHE | GIL_NOTFILENAME | GIL_PERINSTANCE;
    return S_FALSE;
} 

HRESULT CShellIcon::Extract(LPCTSTR pszFile, UINT nIconIndex, HICON* phiconLarge, HICON* phiconSmall, UINT nIconSize )
{ 
    phiconLarge = NULL;
    phiconSmall = NULL;
    return S_OK; 
}