Introduction
If you came across this article then you must have got an error in Visual Studio 2010 after uninstallation of .NET Framework 4.5.

Don't get panic
...the solution is very simple,
How it happened for me
I was installing MVC 4 for Visual Studio 2010 and I got some issues with .NET Framework 4.5. To resolve that issue I uninstalled .NET Framework 4.5. Click here to read the issues caused.
Something went wrong, Visual Studio Stopped working with an Error Message - "Unknown Error".
After some googling I found the solution in MSDN itself
How I resolved
I Just re-installed .NET Framework 4 (updates too if any) as it got uninstalled due to the un-installation of .NET Framework 4.5. That's it. Visual Studio 2010 starts working.
MSDN says that
- The .NET Framework 4.5 replaces the .NET Framework 4. When you install the .NET Framework 4.5 on a system that has the .NET Framework 4 installed, the assemblies are replaced.
- Uninstalling the .NET Framework 4.5 also removes pre-existing .NET Framework 4 files. If you want to go back to the .NET Framework 4, you must reinstall it and any updates to it.
Read more from MSDN