You can gain access to SQL Server 2005 by adding your Windows login to one of the following local groups on the server , depending on if it is default or named instance (replace ComputerName and InstanceName with the actual names)

Default instance: SQLServerMSSQLUser$ComputerName$MSSQLSERVER

Named instance: SQLServerMSSQLUser$ComputerName$InstanceName

You should not have to restart SQL Server to gain access this way.