Resetting my password in windows vista

Hello,
I decided to cancel my password when windows vista home premium boots up and ask you to enter the password.
I can;t enter a password and i cant reset the password and i dont have the original copy of windows vista as i have lost it.
what can i do to resolve this mega issue..please please can someone help me?
ps;i am only a novice on pc,s so pls if you know how to resolve my problem try to do it in simple jargon.
grazia