password help pleeeease!

From: Csurname (csurname@austarnet.com.au)
Date: 06/30/02 

From: "Csurname" <csurname@austarnet.com.au>
Date: Sat, 29 Jun 2002 23:05:35 -0700

My new computer is telling me my password will run out in
10 days. The man at the computer store is on holidays and
noone else knows what my password is! How do I get around
this? I can't change the password until I know what the
old one is.
Thanks
C