VPC and 64-bit Guest support…

http://social.technet.microsoft.com/Forums/en-US/w7itprovirt/thread/8fa1b83d-90ca-449e-92aa-5b20fd82cf1b

http://www.microsoft.com/windows/virtual-pc/default.aspx

http://www.virtualbox.org/

http://www.vmware.com/