Does anyone know how i can hack a users password on windows xp?

Safe mode.
Jack the Ripper.
Backtrack 2.
Austrumi.
Guess and check.

my parents will know if i install one of those programs

Safe Mode.

You don't install those programs... you burn them onto a CD and boot from them.

it depends on what you're looking for on the user's account

Hirens boot cd u could make ur parents your bitch after using that

Restart your PC, go into Safe mode, Create a new user thats an *****, Use that admins powers to change your account into a *****. Reset, go onto your original account and delete the account you just created. Bob's your uncle mate. Iam sure there is a easier way but thats how I did it.

You dont need fancy programs for something as simple as this, but you can use them if you dont understand my way. Basically you own your PC with ***** rights.