C++ Register and Login

#include <iostream>
#include <string>
#include <Windows.h>
#include <stdlib.h>
#include <fstream>
#include <conio.h>
#include <dos.h>

using namespace std;

void main() {
    SetConsoleTitle("Register");
    ShowWindow(GetConsoleWindow(), SW_MAXIMIZE);
    system("COLOR D");
    int Register();
    Register();
}

void scl() {
    system("CLS");
}

void InvalidName() {
    std::cout << "Invalid Name.\n\n";
    std::cout << "Press Enter to Continue." << endl;
    system("PAUSE >NUL");
    if (GetAsyncKeyState(VK_RETURN) & 0x80000 || (GetAsyncKeyState(VK_SPACE) & 0x80000)) {
        scl();
        int Register();
        Register();
    }
    else {
        scl();
        void InvalidName();
        InvalidName();
    }
}

int Register() {
    int continueLoop = 0;
    string username;
    string password;
    string un;
    string pw;
    std::cout << "Minimum (5) Maximum (15)\n" << endl;
    std::cout << "Username: ";
    cin >> username;
    if (username.length() < 5 || username.length() > 15) {
        scl();
        void InvalidName();
        InvalidName();
    }
    else {
        scl();
        std::cout << "Minimum (5) Maximum (20)\n" << endl;
        std::cout << "Username: " << username << endl;
        std::cout << "Password: ";
        cin >> password;

        if (password.length() < 5 || password.length() > 20) {
            scl();
            void InvalidName();
            InvalidName();
        }
        else if (password == username) {
            std::cout << "\nCan't have the password as your username." << endl;
            cout << "Press any key to continue..." << endl;
            system("PAUSE >NUL");
        }
        else {
            ofstream regInfo_;
            regInfo_.open("Register.txt.txt");
            regInfo_ << "Username: " << username << endl;
            regInfo_ << "Password: " << password << endl;
            regInfo_.close();
            std::cin.get();
            scl();

        Login:
            std::cout << ") Register\n" << endl;
            std::cout << "Username: ";
            cin >> un;
            std::cout << "Password: ";
            cin >> pw;
            ifstream read("C:\\Users\danie\\Documents\\Register\\Register.txt");
            getline(read, un);
            getline(read, pw);

            if (un == "REGISTER" || un == "Register" || un == "register" ||
            pw == "REGISTER" || pw == "Register" || pw == "register") {
                scl();
                int Register();
                Register();
            }
            if (un == username && pw == password) {
                scl();
                cout << "Succesfully logged in!" << endl;
                std::cout << "> Press Any Key To Continue" << endl;
                system("PAUSE >NUL");
            }
            else {
                scl();
                std::cout << "Invalid Username or Password." << endl;
                std::cout << "> Press Any Key To Continue" << endl;
                system("PAUSE >NUL");
                scl();
                goto Login;
            }
        }
    }
    return 0;
}