Compiler Error CS0007
This error occurs if the runtime could not be loaded. This could occur if the version of the common language runtime that the compiler attempts to load is not present on the machine, or if the common language runtime installation or configuration is corrupt.
This can happen if the csc.exe.config file was changed. This file is configured during setup and should not be changed. If there is a possibility that the csc.exe.config file was changed, check the file to make sure that the version of the runtime specified in the file is present on the machine. If the correct version is present, it may be corrupted. Reinstall the common language runtime.