Help!! How can i by-pass the sign-up and login form in wordpress MU?

[mariamaria]

I have an existing site - a photo upload website. I have installed wordpress MU so the users can post their photos in a blog. However, to make the user comfortable in using my website, i would like the wordpress MU to use the signup and login information from my photo upload website. The question is "how can i by-pass the sign-up and log-in procedures of wordpress MU and go directly to their blog or admin panel of the blog?" Is there anyone who can help me with these issues?