No, there is no file that's MSBuild that's part of your project. MSBuild is the exe (location varies with version of .Net) and how MSBuild is used varies by version (I should write a blog post on this).

But the schema of an MSBuild file is the same as a VS project file. They are one and the same. When you make changes to the project like I suggested, the changes are made to your project file (csproj, vbproj, etc).

You can edit the file directly in VS.

1. Open the solution as normal in VS.
2. Right-click on the project in solution explorer and select unload
3. Right-click on the project in solution explorer and select Edit
4. Go to the bottom of the file. You'll see the following entries

<!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
       Other similar extension points exist, see Microsoft.Common.targets.
  <Target Name="BeforeBuild">
  </Target>
  <Target Name="AfterBuild">
  </Target>
  -->

If you've modified the project in Project Properties, the node will already be uncommented.
5. When you're done, save the file and close it
6. Right-click on the project in Solution Explorer and select Reload Project

>I tried to search for MSBuild*.* in all my projects folders and sub-folders but can't find it.
>