Recently and with the release of Visual Studio 2015 Update 3 and .NET Core RTM, I decided to uninstall my previous installation of Visual Studio 2015 Update 2 and have a fresh installation of Update 3. So I uninstalled Visual Studio completely and restarted my PC.
Now I decided to uninstall the Microsoft .NET Core 1.0 RC2 VS 2015 Tooling Preview 1 from Control Panel. It gives me the following error several times and then fails:
The specified account already exists.
and here is the error code:
0x80070643 - Fatal error during installation
In the log file, these lines are repeated several times:
[1760:1CA0][2016-07-01T02:30:32]i301: Applying execute package: WebToolsExtensionsVS14, action: Uninstall, path: (null), arguments: ' ARPSYSTEMCOMPONENT="1" MSIFASTINSTALL="7" SKIP_SETUP="1"'
[1760:1CA0][2016-07-01T02:30:39]e000: Error 0x80070643: Failed to uninstall MSI package.
[1760:1CA0][2016-07-01T02:30:39]e000: Error 0x80070643: Failed to execute MSI package.
[247C:2490][2016-07-01T02:30:39]e000: Error 0x80070643: Failed to configure per-machine MSI package.
[247C:2490][2016-07-01T02:30:39]w348: Application requested retry of package: WebToolsExtensionsVS14, encountered error: 0x80070643. Retrying...
As I said in the question, I had Visual Studio 2015 Update 2 uninstalled already, and couldn't uninstall the .NET Core tooling after that.
The fix was to INSTALL Visual Studio 2015 Update 3 and THEN uninstalling the .Net Core 1.0 Preview 1.
After that I successfully installed the Preview 2 version of the tooling and had no errors.