the first time i logged in "that" site and IE prompted me if i wanted to "save [the username and] the password" i replyed "NO"

Now i would like to save [the username and] the password for "that" site but i do not work out how to make IE to prompt me again.

i know that if i change username then IE will prompt me again, but i CANNOT change username

i suppose (but not sure) that if i delete all password (tools>Option>content>auto completion>delete password) then IE would prompt me again, BUT i do not want to delete ALL password

if you can help me
thanks
moluo