ini文件不能写入

AssignFile(f,'ini.ini');
        reset(f,1);
        if FileSize(f) < 48 then
       begin
           Rewrite(f,1);
           buf:='admin';
           BlockWrite(f,buf,12,nw);
           buf:='admin';
           BlockWrite(f,buf,12,nw);
           buf:='a';
           BlockWrite(f,buf,24,nw);
           CloseFile(F);
           ShowMessage('数据成功');