vCard export to a Windows computer

Many times I have received vCards (.vcf) which are automatically read by Address Book with no problem. When I sent my personal vCard to a friend with a Windows system, he received an empty card. If instead of using the vCard coming from the Address Book, I use the vCard coming from Entourage (v 11.4.0), he can read it. Does any body know how to make the vCard from the Address Book work on Windows computers?
Thanks,