I normally customize my Windows installations to run unattended and often end up tweaking the settings that I use for my unattended installations to run the bare minimum of services in order to conserve memory.
After installing an instance of Windows Server 2008 R2 with SP1 and attempting to promote my server to a domain controller, I received the following error message "Failed to install Active Directory Domain Services binaries".
Well, after a little digging, I discovered that I had disabled the Remote Registry Service in the Services Control Panel Applet. Interestingly enough, this service does not sound like a necessary requirement for promoting a server to a domain controller, but it is what it is!!
In any case, after setting the Remote Registry Service to start Automatically and rebooting my server, I was able to successfully run dcpromo to upgrade my server to a domain controller!