If you’re not using Active Directory, your “Local Security Policy” dictates things like password complexity rules, account lockouts, and password expiration. To turn off password expiration:
1) Login as Administrator or a user with Administrator rights
2) Launch “Local Security Policy”: Start > Administrative Tools > Local Security Policy
3) Expand “Account Policies”
4) Select Password Policy
5) Set Maximum Password age to “0″
Source : Ryan’s Tech Notes
In order to connect to a windows VPS remotely , you need to use a software named “Remote Desktop Connection” which is bundled with all versions of windows.
under windows XP it is located under : All Programs –> Accessories –> Communications
under windows Vista it is located under : All Programs –> Accessories
after running this software you will see the following window , enter the IP or host name of your VPS into the computer filed and click on Connect.
after a few seconds a new windows will be opened and you will be asked for the username and password , enter the username and password which is provided by your windows VPS provider. usually the username is Administrator.
if you enter the login details successfully , the desktop of windows VPS will be shown to you.
After you are logged into VPS , follow the below instructions :
Press CTRL+ALT+END buttons simultaneously , the following menu will appear :
Click on Change Password :
Fill the fields and click on OK.
Done 
There are a few scripts available on net which allow you to change a linux user password from PHP. but all of them are very complex and hard to implement , so after some hours of work , I’ve written this PHP script it is very simple , in order for this to work you need to allow your webserver to run sed command as root through sudoers , or allow your webserver to write on your /etc/shadow file.
$username='USERNAME';
$password='PASSWORD'; // New Password
$sed='/bin/sed'; //Path to sed command
$salt = substr($username, 0, 2);
$pass_crypt = crypt($password, $salt);
$pass_crypt=str_replace("/","\/",$pass_crypt);
system($sed." -i 's/".$username.":[a-zA-z0-9/$\.]*/".$username.":".$pass_crypt."/g' /etc/shadow",$retval);
If you have never set a root password for MySQL, the server does not require a password at all for connecting as root. To setup root password for first time, use mysqladmin command at shell prompt as follows:
mysqladmin -u root password NEWPASSWORD
However, if you want to change (or update) a root password, then you need to use following command
mysqladmin -u root -p'oldpassword' password newpass
For example, If old password is abc, and set new password to 123456, enter:
mysqladmin -u root -p'abc' password '123456'
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