Hi Josef,
first, this is a german speaking forum. The english forums are located here:
http://social.technet.microsoft.com/Forums/en-US/winserverhyperv
About your question: It it recommended to have at least the PDC-Emulator role on a physical box. Within your environment it would be the parent. In the same sentence I have to say that it is not recommended to have any other role activated except the Hyper-V
role. So domain controller functionality and Hyper-V on one box is not recommended but it will work.
The guest OS with Remote Desktop services enabled is a good choice. I expect that you to not have a mass of users one one box?!
There is an article about running domain controllers within a Hyper-V (VM) environment available here:
http://technet.microsoft.com/en-us/library/virtual_active_directory_domain_controller_virtualization_hyperv(WS.10).aspx
Conclusion: Hyper-V and AD on one box will work but is not recommended.
Peter Forster, MVP Virtual Machine, Austria http://www.base-it.at