>I have NT4 IIS4. Do I have to have 2 secure Certificates
>for 2 different domain name web sites.

As long as both domains are hosted on the same NT server, you can bind the certificate to the different IP addresses or you can bind the certificate to all IP addresses on the server.

Highlight your web site and look at Properties - Directory Security - Secure Communications - Edit - Key Manager. Highlight the installed certificate and choose Key - Properties - Add/Edit to either add another IP address or change the existing to Any Unassigned.