Err, safe mode doesn't help you. You still have to login! A lot of off-the-shelf computers simply don't have an admin password set. Grossly irresponsible of manufacturers, but that doesn't usually stop them. Press ctrl-alt-del twice at the welcome screen to get the traditional login box, the try Administrator as the username, with no password. Worth a shot.
A utility like
this can reset or remove users' passwords. Read the instructions though, it's a very powerful tool.