uses ShellApi;
procedure TForm1.Button1Click(Sender: TObject);
var
ShortName: array[0..255] of char;
begin
OpenDialog1.Filter:= 'Archivos de registro|*.REG';
with OpenDialog1 do
if Execute then
begin
GetShortPathName(PChar(FileName), @ShortName, Length(FileName));
ShellExecute(Handle, 'open', 'C:\HANDLER.CMD', PChar(@ShortName), nil, SW_NORMAL);
end;
end;