It's been a year since my exchange 07 install and the automatically created certificate has expired. How do I extend/recreate the certificate?

are you wanting to go with a trusted certificate? You'll need to generate a new cert from a 3rd party company, an internal CA, or the IIS resource kit. http://www.somacon.com/p42.php Then you'll need to use import-exchangecertificate and enable-exchangecertificate powershell cmdlets.