administrator password

Ok here it is. I just bought a Computer from a business that went out of business. The 1st time I turned it on windows loaded. Its winxp professional. I tried to load Mozilla I hate IE, and I got a error need administrator password. So I went in to User setting and tried to remove or change the admin password but that is password protected. so I restarted and now the windows login comes up with a weird User name and a blank password.I have no Idea what the password is. I tried to restart in safe mode to fix that but now im am stuck at the log on to windows screen. So now I cannot get into the OS to do anything. I did not get a copy of XP with it. And I lost my copy for my other computer. So I just can reload it. Hope that makes sense any tip would be appericated