If the computer is using Firefox as its default browser, Google is the default home page. If it's Internet Explorer then go to Tools - Internet Options - General. Have a look to see what is set as the Home page. This can be set to be the current page, blank or the default - which is probably MSN. The X is only there to shut Internet Explorer and shouldn't crash the computer so there must be another problem. A thorough scan for viruses, trojans and other malware would be a good idea.