How to give ASP.NET access to a private key in a certificate in the certificate store?

I have an ASP.NET application that accesses private key in a certificate in the certificates store. On Windows Server 2003 I was able to use winhttpcertcfg.exe to give private key access to the NETWORK SERVICE account. How do I give permissions to access a Private Key in a certificate in the certificate store (Local ComputerPersonal) on a Windows Server 2008 R2 in an IIS 7.5 website?