Certificate types are not available

Hello everyone,

I am sorry for my bad English.

My CA is on Windows Server 2008 R2 and is a domain controller also.  Clients are Windows 7. All clients connected to DC.The Certificate Authority is an Enterprise CA. When i try request for certificate on the client computer mmc>certificates>personal> task >

Certificate types are not available -  When creating computer certificate. It may also be that my installed CA is not allowing generation of "Computer" certificate types. Please help me...