will75 (4/30/2013)
I have tried this. The problem is the user I login with (my domain account) when I use command line does not have right to grant sys_admin right. I am already in the administrator group on the server. I think the problem is the BUILTIN is not in SQL.
If you are part of Windows Admin Group on that machine, and you start MS-SQL on single user mode, you should be able to reset sa:
Disaster Recovery: What to do when the SA account password is lost in SQL Server 2005:
Now, above process is for SQL2005, but I do believe still applies for SQL2008.