Lost Administrator Login Rights

Just bought a new Dell desktop. Setup went well. Vista got up and running just fine. A couple of weeks past by and suddenly I lost my administrator login – it doesn’t recognize my password anymore. Spent hours w/Dell. They want me to copy everyone elses files – there are 3 other user in my family, and then wipe the hard drive and start all over. I will loose all my files, since I can’t login and copy them out. Any solutions out there that will let me reset the administrator, or whatever it is I need to do?