Even though I think that your question is really OT as the "feature" in IE you are asking about can only be set in the configuration settings of IE, which a (guest) user on a shared machine might not be allowed to change I would suggest that you compose the name for the login and passwd field randomly and send it along with a session Id to the client. You have to temporarily store the session id along with the name of those fields to be able to process the form fields in return as every request will then deliver different named fields.

Have a nice day
All decision is left to your taste