BUILTIN\Administrators accidently removed Hi, so recently when trying to fix another bug within my sql server 2008 R2 db I removed the BUILTIN\Administrators login from sysadmin. Now it will not let me change anything winthin the database. Also I do not have the SA account password to log in as that user to change/ add any permission.

Can anyone help me add the BUILTIN\Administrators login back into sysadmin or find a way to alter the database using my windows account?
Start the SQL Server service in single-user mode (by using the -m startup parameter).  When you do this, all members of the local administrators group will have sysadmin rights.  Provided you are a member of that group, you should be able to do whatever sysadmin actions you need.

Take a look at Database Engine Service Startup Options for documentation.

Edit:  To start SQL Server in Single-User Mode, please see this documentation.