Issues with uninstalling and re-installing SQL Server 2008 R2 I have installed SQL Server 2008 R2, and was able to login and also create a database and everything.

When I was facing some problems with connecting my .NET project with SQL Server, I created some new accounts in SQL Server.

For some reason I uninstalled it. But later when I re-installed, I was not able to login with the "SA" account. I still see a few of the other user accounts that I created earlier.

Is there any way to completely uninstall SQL Server 2008 R2 and successfully install new copy and login?
Log in with your Windows account and enable the SA login again.  You'll probably need to configure the SQL Server for mixed mode authentication as well.

If you decide that you do want to reinstall SQL, after uninstalling it you'll need to remove the database files then you can reinstall.  SQL leaves the databases alone when you uninstall so that you don't loose any accounts or data when reinstalling.