Ok, try this:

Backup and then delete your config.php file. Then run the Moodle setup. It will detect that you don't have a config.php file and it will prompt you for all the values that it needs to create one.

Does that work?

***

Something to play with if the above doesn't work:
(Note: Tread with caution - I'm not a Moodle developer, or even a PHP programmer!)

To me the "Undefined property: stdClass::$dbfamily in E:\moodle\lib\setuplib.php on line 281" error says that a valid value for dbfamily has not been returned by the $dbtype switch statement on line 243 of the moodle\lib\setuplib.php file and there is no 'default' option in the switch statement to catch any invalid values. So you're getting the error because you haven't specified a valid value for $CFG->dbtype in the config.php file.

That $dbtype switch statement only checks for 7 values: 'mysql', 'mysqli', 'postgres7', 'mssql', 'mssql_n', 'odbc_mssql' and 'oci8po'. Whatever you have specified as your dbtype in the config.php file doesn't match one of those 7 values and that's why you're getting the error message.

Try adding an extra default statement to that $dbtype switch statement in the setuplib.php file:

switch ($dbtype) {
    case 'mysql':
    case 'mysqli':
        $CFG->dbfamily='mysql';
        break;
    case 'postgres7':
        $CFG->dbfamily='postgres';
        break;
    case 'mssql':
    case 'mssql_n':
    case 'odbc_mssql':
        $CFG->dbfamily='mssql';
        break;
    case 'oci8po':
        $CFG->dbfamily='oracle';
        break;
    default:
        echo "You must specify a valid value for $CFG->dbtype in config.php";
        break;
}

Then add an if (empty(...)) check to the switch ($dbtype) statement in the set_dbfamily() function in your \Moodle\lib\setuplib.php file:

function set_dbfamily() {

    global $CFG, $INSTALL;

    // Since this function is also used during installation process,
    // i.e. during install.php before $CFG->dbtype is set.
    // we need to get dbtype from the right variable
    if (!empty($INSTALL['dbtype'])) {
        $dbtype = $INSTALL['dbtype'];
    } else {
        $dbtype = $CFG->dbtype;
    }

    switch ($dbtype) {
        case 'mysql':
        case 'mysqli':
            $CFG->dbfamily='mysql';
            break;
        case 'postgres7':
            $CFG->dbfamily='postgres';
            break;
        case 'mssql':
        case 'mssql_n':
        case 'odbc_mssql':
            $CFG->dbfamily='mssql';
            break;
        case 'oci8po':
            $CFG->dbfamily='oracle';
            break;
    }

    if (empty($CFG->dbfamily)) {
        print_error('missingdbtype');
    } else {
      return $CFG->dbfamily;
    }
}

And then add this to the bottom of your \Moodle\lang\en_utf8\error.php file:

$string['missingdbtype'] = 'An invalid value was specified for the dbtype parameter in your config.php file';

What happens when you run the Moodle setup after making these changes?

WARNING! I haven't extensively tested all this and I'm not a Moodle developer... and there could be better ways to do the error handling... so don't try this on a production box!

Before you deleted the config.php file did you check that you had set it up correctly?

The $CFG->wwwroot variable must contain the web address for your site, e.g.:

$CFG->wwwroot = 'http://yourdomain';
or
$CFG->wwwroot = 'http://yourdomain/moodle';
or
$CFG->wwwroot = 'http://localhost/moodle';

And $CFG->dirroot must contain the actual path where you extracted the Moodle archive to, e.g.:

$CFG->dirroot = 'C:\Moodle';

And $CFG->dataroot must contain the actual path to your MoodleData folder, e.g.:

$CFG->dataroot = 'C:\MoodleData';

What web server are you using? Apache or IIS?
Have you set it up for your Moodle website? E.g. did you create a virtual directory in IIS?