Q:

Can't log into SQL server after changing computer name

I installed Windows Server 2008 and SQL Server 2008 R2, after joining to domain I changed computer name and mistakenly I deleted the administrators group from SQL Server login users and now I am not able to login.
Any suggestion?

A:

I know this is old but I just used the Gui instead.
Step 1. Start SSMS
Step 2. Select the server name drop down and click browse more.

step 3. select local or network tab based where the server is and expand Database engine and select the correct computer name\sql server

A:

Follow the steps in this article: http://v-consult.be/2011/05/26/recover-sa-password-microsoft-sql-server-2008-r2/
Basically you have to modify the SQL Server Service settings so that it starts in admin mode. This will only allow one connection to it. Once you start it up you can create a new sysadmin user that you can use from then on.
Also I do know that you need to run certain scripts on a SQL Server if you change the hostname of the server. You should find them if you google them.

A:

If you have mixed mode authentication enabled on the SQL Server instance, you can login using the sa account, with the password that you specified during installation.
If you have only Windows authentication enabled, I'm not sure. You could try running setup again and seeing if it will let you change the authentication mode, but somehow I doubt that it will let you do anything without first connecting to the instance with your Windows identity.
As a last resort, you could try uninstalling and re-installing the SQL Server instance, then re-attaching all your databases.

