I am running seti@home on boinc. I also want to be associated with BBC climate change and Einstein project. However, i am unable to associate them with my boinc manager. When I downloaded boinc from bbc site it replaced seti@home. How can I run multiple projects on the smae boinc manager. Plz help. Thank you.

The BBC site is setup with a modified version of BOINC to automate things for large masses of people who have never heard of distributed computing, BOINC, or any other complicated words.

Clicking their download button has downloaded this special version.
So now you need to Uninstall it, then reinstall your original version. And you'll find your old SETI files are still there.

If you want to be "associated" with other projects, you do this by Attaching to these projects, with the option in the menu.