Internet Explorer, save website password problem

Hi guys, I have my Vista machine set to store passwords for logging on to
websites, the problem I have is that I told IE7 not to store one particular
site's password, which is exactly what it has done, but now I have changed
my mind and want it to store that password, but I cannot seem to find how to
tell it to do so. I cannot find where it stores the logon data, and as I
have told it not to store the info on this site I cannot now get it to ask
again? I know it must be obvious, but it is driving me crazy??
Any help would be most welcome
Peter