CaCert certificate migration

hi, our site www.delin-elettronica.it is on a linux server and SSL is
certified by www.cacert.org

Is it possible to move certification to a SBS R2-Sharepoint 3.0 IIS 6.0 ?

I tried to import crt file in MMC snap-in and also configured IIS site to
use that certificate but I can't find a way to import also the private key.
Is it possible with certUtil ?
Can someone help me?