You will need your password to do it. Go to your old teams page at the Seti@home site and click Quit team the next page will ask for your Seti Email and Password. If you dont know it they will send it to your Seti email address, this address is still active isnt it? When you have it you can quit your current team. Then you go to the Anandtech team page and click join fill in the info and you should be done. When you joined your current team Seti sent you your password so you may still have it in your old Emails.