Visual Studio 2015 RC Community will not install, says it is already installed

Question

As the title implies, I am not able to install Visual Studio 2015 RC Community, and I keep getting the following errors. For the record, I am on Windows 8.1 Professional.

Answer 1

I have been experiencing a similar problem (trying to get rid of Visual Studio 2015 Ultimate CTP and install Visual Studio 2015 Professional instead). I had troubles uninstalling the CTP and the Professional edition kept complaining that the Ultimate version is already installed. Unfortunately, none of the proposed solutions worked for me (forced uninstall, TotalUninstall, MS Install and Uninstall diagcab, no DevDiv registry key...).
But I finally found a solution suitable for my case - using msiinv utility.

The msiinv tool is a tool which will list all installed msi on your OS. In that way you can check them and if you want to remove any of them, you may try the msiexec /x to remove that component.

Basically all that needed to be done is described in this blog post:

1) Extract the contents of msiinv.zip to the folder c:\msiinv on your system
2) Click on the Start menu, choose Run, type cmd and click OK
3) Type this command: c:\msiinv\msiinv.exe -p > c:\msiinv\msiinv_output.txt
Note: This command must be run from a cmd prompt or it will not create a log file as expected.

These steps will create a text file named c:\msiinv\msiinv_output.txt with a list of each product that Windows Installer thinks is installed on the system. Then you can open the text file in any text editor and search the list of products for the name of the product that setup told you to uninstall.

In the output there should be a part looking like this (changed to VS2015 Ultimate):

Microsoft Visual Studio 2015 Ultimate CTP
      Product code: {EF2A2E8D-E03C-370E-810F-449BECDE2240}
      Product state: (5) Installed.
      Package code: {another GUID here}
      Version: 14.0(...)

Now we have the Windows Installer product code and we can use that to uninstall the product by running msiexec /x (make sure that you include the curly braces in this command line). If the product is actually installed on your system you will see a progress screen and uninstall will complete.

I have repeated the steps also for Microsoft Visual Studio 2015 Ultimate CTP - ENU, just to be sure. The Professional edition installer then launched and finished successfully.