If you can not Use the link on sign in page.
You can download some msn password recovery software,
Here I would to recommand MSN Password Recovery 5.0 is the best Messenger password recovery tool that instantly recovers and decrypts forgotten or lost passwords for MSN Messenger. http://www.recoverlostpassword.com/products/msnpassword...
Hope can help you.
Yes, like "Ijack" said clicking the "forgot the password" link and by following the hints or recovery email adress, you will be able to get back or reset your forgotten password.
If you can't remember any information with regards to your account, do not worry. You can rely on this password recovery software to "see" part of the username and password. Note: it's not freeware, after you confirm it does detect your lost account info, then it's your option to buy it or not.