uses
ShlObj;
procedure RefreshDesktop1;
begin
SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, nil, nil);
end;
tested on Win 7 100% works guaranteed.

uses
ShlObj;
procedure RefreshDesktop1;
begin
SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, nil, nil);
end;
tested on Win 7 100% works guaranteed.