I've just installed VS2015 Preview and afterwards it gave me the option of installing additional software, including the Android Emulator. Unfortunately the company network went down before the download completed so the installation failed, and it didn't give me an option to retry.
Where can I download the emulator, or how can I relaunch the setup for Additional Software?
You can use the Microsoft Visual Studio 2015 Preview Secondary Installer to install VS Android Emulator.
Try out following steps to launch Secondary installer and install VS Android Emulator:
Open Add\Remove program, Control Panel --> Programs --> Uninstall a Program. Click change to launch Secondary Installer