1) Did you double check that you have .NET 4.0 installed? If you got it from Steam, you should have 4.0 already. The system error message is usually related to an earlier version of .NET. Probably the easiest thing to do is to download the .NET installer from here: http://www.microsoft.com/downloads/details...9f-b21f31ab88b7 ...and install. *Ignore this step if you are running Windows 7. Windows 7 has the correct version of .NET pre-installed.* =========================================