Compiler failed to execute.

Unity isn't working at all. I've been having this issue for three days, with no way to resolve it. I've tried uninstalling, reinstalling, uninstalling with an uninstaller, everything. I checked my antivirus as well, nothing.

The error messages:

Compilation failed because the compiler could not be executed!

Could not start compilationWin32Exception: ApplicationName='"C:\Program Files\Unity\Editor\Data\Mono\bin\mono.exe"', CommandLine='"C:\Program Files\Unity\Editor\Data\Mono\lib\mono\unity\smcs.exe" @Temp/UnityTempFile-db4ba4d7837092447ac5a03530af8a39', CurrentDirectory='C:/Users/Me/Documents/Subnautica2D/Assets/..' System.Diagnostics.Process.Start_noshell (System.Diagnostics.ProcessStartInfo startInfo, System.Diagnostics.Process process) System.Diagnostics.Process.Start_common (System.Diagnostics.ProcessStartInfo startInfo, System.Diagnostics.Process process) System.Diagnostics.Process.Start () (wrapper remoting-invoke-with-check) System.Diagnostics.Process:Start () UnityEditor.Utils.Program.Start () (at C:/buildslave/unity/build/Editor/Mono/Utils/Program.cs:33) UnityEditor.Scripting.Compilers.MonoScriptCompilerBase.StartCompiler (BuildTarget target, System.String compiler, System.Collections.Generic.List`1 arguments, Boolean setMonoEnvironmentVariables) (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/MonoScriptCompilerBase.cs:31) UnityEditor.Scripting.Compilers.MonoScriptCompilerBase.StartCompiler (BuildTarget target, System.String compiler, System.Collections.Generic.List`1 arguments) (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/MonoScriptCompilerBase.cs:18) UnityEditor.Scripting.Compilers.MonoCSharpCompiler.StartCompiler () (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/MonoCSharpCompiler.cs:43) UnityEditor.Scripting.Compilers.ScriptCompilerBase.BeginCompiling () (at C:/buildslave/unity/build/Editor/Mono/Scripting/Compilers/ScriptCompilerBase.cs:47)

I've used unity for over two years, and this has never happened. Please help, your help will be much appreciated.