Multiple email addresses and XP Pro

I set-up individual start-up accounts for my wife and me with password protection.

I have a single ISP account/username with 4 alias's eg., alan@etc, marg@etc, sales@etc, tech@etc.

My wifes account contained her email account/address only, mine contained my 3 addresses only.

How can I get my wife's Outlook Express to respond only to her alias. I.e, receive only her messages and not mine?

As above only on my account?

I have tried message rules, different identities etc with no luck.

We both have Administrator privledges.

Alan J.
Cheshire UK