At Namecheap, in order to issue or reissue the next year SSL certificate, you may re-use the same Certificate Signing Request that you previously generated the previous year for the original SSL certificate (althouth it is not recommended). Sentigo (formerly Comodo) will only issue certificates which last (expire in) one year, even though you may purchase multiple years in advance. Namecheap sells these and reissues them. You can expose the old CSR at Namecheap under manage products, reissue. Copy the original CSR text into your windows clipboard, click Re-issue, and insert/paste the CSR into the text box. Follow the instructions for how to confirm you are the owner or person who controls the domain where the certificate will be installed. Use email.

Sentigo issues the certificate (cert.crt) for your website via email in a zip file. Save to your hard disk and extract the files. Ignore the bundle file. That is for Linux distros. We will be using the certificate.crt file

Open IIS internet information services on Windows 2008 R2. Select the server name at the upper left of the Microsoft management console snap-in. In the Middle window, Double Click to Select the “Server Certificates” icon. In the far right pane, click the text link “Complete Certificate Request.” In the popup property page, click … to Browse for the cert.crt file that you extracted from Sentigo's email to your server's hard drive. You may need to switch the file filter to *.* for all files to see and select certificate.crt. Enter a friendly name for the Server name of the Certificate such as mx.mydomain.com and submit to continue.

While in IIS, expand sites and select the default website. Select Bindings on the far right pane. Select the entry for SSL Port 443 binding and use the dropdown box to select the friendly name of the newly issued SSL certificate. Click ok, or apply, ok whatever the button name is.

You may or may not need to restart IIS service for the certificate change to take effect.