Login/slightly different, but it seems equally hard to find

Ok,
Now im trying to make a login page, so that people who have lost the cookie on there computer can retrieve it, any ideas?

This is the setcookie command I use:
setcookie("CookieID", mysql_insert_id(), time()+94608000, "/");
I need the cookie to set the user specif information based on their username and password

Again any help is great.