Re: Urgent help needed! Regarding btinternet email
As well as using the links posted on this thread, it is also worth installing an email client such as Thunderbird or Microsoft Live Mail. This will allow you to add all you contacts to the email client and download all your emails onto your computer.
This allows you to delete your contacts that are on BTYahoo webmail. While it won't stop the account being hacked again it will stop your email contacts being spammed.
This will also allow you to back up your contacts and emails in case of problems during the migration of BTYahoo to the new BT Mail which is due to take place later this year.