The access code for Logmein is nothing more but the password of a local windows user account called Logmeinremoteuser. It has a special flag, so it does not show up in the XP fast user switch screen or in control panel by default /same way as built-in administrator account/ but you can easily reset the password this way:

On NT based systems:
Start > Run, type ‘control userpasswords2’ then select the user ‘Logmeinremoteuser’ and click reset password… the new value you type in there will be your new Logmein Access Code.