Hello guys!

Anyone that has knowledge of modifying wordpress, please help.

I am working on my site using the WP2.2. The concept is there will be five authors and each author will post blog and each post is separated according to the author that posted the said articles.
What i did is, i install five WP 2.2 for the five authors so that it will only display the articles by author. My problem is they have different login. What i need is whenever a user is log-in on the other page there is no need for them to login on the other blogs. So in 5 blogs if they want to comment, they need to login only once. The five blogs share one database but they have different tables because i set different prefixes for each author.
Is it possible for that case to work in 5 different blogs installed? Please help and please do give recommendation. thanks a lot.