Altering the "WindowsXP" remember password option

I have in the past used the "WindowsXP" Remember Password Option on various sites. Unfortunately I have had some of my accounts hacked. I now want to turn off the remember password option at those sites where I have used it. I am quite happy to remove t
he file where the remembered files are held in it's entirety but I can't find any reference anywhere as to how I can turn the option off, or remove the file.
Can anyone help me with this?