I downloaded the full ISO for Visual Studio Ultimate CTP 6. The installation program got to about the 90% mark, gauging by the progress bar, and just stuck there. There wa
Same thing happened to me, and I also tried to terminate secondary process from task manager. Do not do that. It is not a solution, but rather a hack which may cause issues later. In my case, I was not even able to uninstall Visual Studio. I tried both web installation and ISO, same issue.
Here is how it worked finally. I restored my Windows 7 to earliest restore point as possible, when there was nothing installed, so I was sure that there would be no conflicts between the different tools (Java, Android API, etc.)
I started the installation of Visual Studio 2015 Community Release Candidate at 10 p.m. At 7 a.m., it was working on Android API 19-21. A hour later, it was finally preparing Visual Studio.
This means that all you need to do is to actually wait 8 to 9 hours. Don't terminate the secondary installer at risk of breaking your Visual Studio; just wait.