if ($_POST['req_cash'] == 'requested' && $_POST['submit'] == '  Request Cashout  ' && is_numeric($_POST['amount']) && $_POST['amount'] >= $min_cashout && $_POST['amount'] <= $roi_cash) {

What is WRONG!

Thank you!!

Suggest that you echo each of the variables to see if they are what you thought they were.

<?php // Connects to your Database 
 mysql_connect("your.hostaddress.com", "username", "password") or die(mysql_error()); 
 mysql_select_db("Database_Name") or die(mysql_error()); 
 //This code runs if the form has been submitted
 if (isset($_POST['submit'])) { 
 //This makes sure they did not leave any fields blank
 if (!$_POST['username'] | !$_POST['pass'] | !$_POST['pass2'] ) {
 		die('You did not complete all of the required fields');
 // checks if the username is in use
 	if (!get_magic_quotes_gpc()) {
 		$_POST['username'] = addslashes($_POST['username']);
 $usercheck = $_POST['username'];
 $check = mysql_query("SELECT username FROM users WHERE username = '$usercheck'") 
 or die(mysql_error());
 $check2 = mysql_num_rows($check);
 //if the name exists it gives an error
 if ($check2 != 0) {
 		die('Sorry, the username '.$_POST['username'].' is already in use.');
this makes sure both passwords entered match
 	if ($_POST['pass'] != $_POST['pass2']) {
 		die('Your passwords did not match. ');
 	// here we encrypt the password and add slashes if needed
 	$_POST['pass'] = md5($_POST['pass']);
 	if (!get_magic_quotes_gpc()) {
 		$_POST['pass'] = addslashes($_POST['pass']);
 		$_POST['username'] = addslashes($_POST['username']);
 // now we insert it into the database
 	$insert = "INSERT INTO users (username, password)
 			VALUES ('".$_POST['username']."', '".$_POST['pass']."')";
 	$add_member = mysql_query($insert);
 <p>Thank you, you have registered - you may now login</a>.</p>

nextdate your both post are totally different.
POst your exact question with code and error you are getting.
BTW use [ code ] tag given in editor to post your code.