Convert Apache SSL Private Key to IIS Private Key

To convert private key being used with Apache (usually .key) to IIS private key (.pfx) use the following command:

openssl pkcs12 -export -out private.pfx -inkey private.key -in public.crt

You'll be asked for the password to unlock current private.key (in case it's password protected) and another password to be assigned to the new private.pfx file.