Vista Basic Problems

Hi All

I have just bought a comp with Vista Basic and have run into a problem. I
installed an email program (incredimail) for my wife and Avant Browser for
myself and there are 4 different profiles on the computer. When logged onto
my profile I can launch Incredimail and I can see all my wifes emails. When
I'm in my wifes profile I can launch Avant and I can see all my bookmarks,
history, google searches etc. Obviously this is a potential divorce
situation so does anyone have any ideas on why this might be happening.

Thanks