Recently I got a new Windows 10 computer at work and tried to open an Visual Studio 2010 project, and then I got a web server error as follows:

Configuring Web http://localhost:64886/ for ASP.NET 4.5 failed. You must manually configure this site for ASP.NET 4.5 in order for the site to run correctly. ASP.NET 4.0 has not been registered on the Web server. You need to manually configure your Web server for ASP.NET 4.0 in order for your site to run correctly.

Well, this type of error usually means that the IIS web server is installed after the .NET framework is installed, and the simple fix is to run aspnet_regiis.exe command (run as Administrator), but only when I was told by my computer that aspnet_regiis.exe is not supported in Windows 10. It turned out that I need to go through the “Turn Windows features on or off” interface to enable the support of ASP.NET 4.0.

Windows 10 hides the interface of additional features by default, in order to access the interface, you need to follow the steps below:

1. Click Windows icon and choose Settings

2. In Settings windows, click Apps & features, then scroll all the way down until you see Programs and Features under Related Settings.

3. Click Programs and Features, and you should see the familiar window like this:

4. Click Turn Windows features on or off, then scroll down to Internet Information Services, then expand World Wide Web Services->Application Development Features, then check ASP.NET 3.5 and ASP.NET 4.6.

5. Exit the window and reboot your computer.

Unfortunately, it didn’t fix the issue (screaming, screaming…). After some more investigation, it turned out this error was caused by a bug in Visual Studio and the workaround is to download a fix from Microsoft, according to this MSDN blog post: https://blogs.msdn.microsoft.com/webdev/2014/11/11/dialog-box-may-be-displayed-to-users-when-opening-projects-in-microsoft-visual-studio-after-installation-of-microsoft-net-framework-4-6/

After I installed this fix, I was able to create a virtual directory for my application and launch the application in Visual Studio.

Hope this helps.