Purpose: If you don't want to put a SQL db into single user mode, you can try the following to give yourself permission to a SQL instance.
The following will open a command prompt as the built in security principal "System" using PSExec.
psexec -i -s -d cmd
From there open SQL management studio from within that command prompt.
ie:
c:\Program Files (x86)\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\Ssms.exe"
I came up with this independently, but a simple google search will show you others have figured it out as well.
Should be able to now give yourself permissions to log on now depending on how the SQL was initially configured. If this doesn't work you will have to
Start the instance of SQL Server in single-user mode by using either the -m or -f options. Any member of the computer's local Administrators group can then connect to the instance of SQL Server as a member of the sysadmin fixed server role.
http://msdn.microsoft.com/en-us/library/dd207004.aspx
