Setting up different email clients for different users

I am running Win XP Prof SP2. I have configured user accounts for all four of my family members. My requirement is to have Outlook Express as default email client for all users except myself. I want to keep a different email client as default for myself. When I try to configure in that manner, any change made is automatically reflected for all four users.

Help required to solve this problem. I feel that by some registry tweak, this can be accomplished.

Please help......