sharepoint site error: HTTP error 503. The service is unavailable

I got this error when I was trying to access teh sharepoint central administration. Trying to find out what did I change to cause this, I realized that this was after I changed the windows password. I found a simple and short step by step guide to solve the problem and it was effective.

The link is : https://nassharepoint.wordpress.com/2009/01/13/sharepoint-site-error-service-unavailable-http-error-503-the-service-is-unavailable/