If you have.NET Framework v4 installed, then
C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe somefile.cs
or
C:\Windows\Microsoft.NET\Framework\v4.0.30319\msbuild.exe nomefile.sln
or
C:\Windows\Microsoft.NET\Framework\v4.0.30319\msbuild.exe nomefile.csproj
If you have.NET installed, it is likely, the FrameworkDir variable is almost certainly set, so:
%FrameworkDir%\v4.0.30319\csc.exe ...
%FrameworkDir%\v4.0.30319\msbuild.exe ...