Unity 3d 4.6.f3 Could not find Csharp Compiler. Please help me?

Could not start compilationApplicationException: Unable to find csharp compiler in C:/Users/Rae Rae/Downloads/UnitySetup_update-4.6.4p3/$_OUTDIR/Data/Mono\lib/mono/unity_web
UnityEditor.Scripting.Compilers.MonoCSharpCompiler.GetCompilerPath (System.Collections.Generic.List`1 arguments) (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/MonoCSharpCompiler.cs:73)
UnityEditor.Scripting.Compilers.MonoCSharpCompiler.StartCompiler () (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/MonoCSharpCompiler.cs:44)
UnityEditor.Scripting.Compilers.ScriptCompilerBase.BeginCompiling () (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/ScriptCompilerBase.cs:47)

a antivirus software might have deleted it or you by accident. you may have to re-download the whole unity or search the file and see if you can find it to download then just put it in the dir that it wants it to be in. or it may be a easy way a antivirus software is blocking unity to find it. maybe just use javascript?