This FAQ explains the steps needed to install a renewed SSL Certificate on a Windows Server 2003 OS. The easiest method is to simply remove the current SSL for the web site in IIS and then go through the normal installation of the renewed certificate in the same way as installing a new certificate. The installation of a renewed certificate is carried out via the use of a new PFX file that can be generated from the 1&1 Control Panel. You will have to generated a new PFX file with the original SSL Private Key and the new certificate.Read through the procedure once before completing the steps to familiarize yourself with the process.
You may now create the PFX file for the renewed certificate from the 1&1 Control Panel. Check the date on the SSL details page to make sure that the 1&1 Control Panel is showing the renewed one (the expiration date should be at least one year from the current date if just renewed). Enter the original SSL Private Key issued for the SSL certificate when you first ordered it and generate the new PFX file. Reference How do I generate the PFX file? for more information.
When the new PFX file has been generated, you may install the renewed SSL by following the same steps as How do I install a dedicated SSL certificate on a Windows Server 2003 OS? just as if it were a newly ordered SSL certificate.