The vswitch utility can be used to switch between Microsoft® SQL Server™ 2000, SQL Server version 6.5, and SQL Server version 6.0 as the active version of SQL Server.
vswitch -SwitchTo {60 | 65 | 80} [-Silent {0 | 1}]
The vswitch utility affects only the default instance of SQL Server. It does not affect named instances of SQL Server 2000. For more information, see Multiple Instances of SQL Server.
For information about where to find or how to run this utility, see Getting Started with Command Prompt Utilities.