The default installation of Unified Remote Server does not enable mouse and keyboard control on Windows login (it does however work when the computer is locked). To enable this functionality you must install Unified Remote Server with the "Service" feature enabled. Note that this feature is still experimental and may have some bugs.
Download the latest version of Unified Remote Server. http://www.unifiedremote.com/download
Proceed to finish the installation. Note you may have to restart your computer.