Fix: "Failed to generate a user instance of SQL Server due to a failure in starting the process for the user instance. The connection will be closed"

Solution:

Step 1: Enable User Instances for SQL Server installation.

a. Go to Query Window in SQL Server Management Studio and type this:

exec sp_configure 'user instances enabled', 1.

b. Then type this: Reconfigure and run.

c. Restart the SQL Server.

Step 2. Deleting old old User Instances.

a. Go to the following path in your local machine and DELETE all files and folder under that folder:

C:\Documents and Settings\YOUR_USERNAME\Local Settings\Application Data\Microsoft\Microsoft SQL Server Data\SQLEXPRESS

Here, YOUR_USERNAME indicates the current username in your computer.