Run the installation of the SQL Server 2000 In the Existing Installation dialog box, click Upgrade your existing installation, and then click Next.
In the Upgrade dialog box, you are prompted as to whether you want to proceed with the requested upgrade. Click Yes, upgrade my to start the upgrade process, and then click Next. The upgrade runs until finished. In the Connect to Server dialog box, select an authentication mode, and then click Next.

If you are not sure which mode to use, accept the default: The Windows account information I use to log on to my computer with (Windows). In Start Copying Files dialog box, click Next. Now your Sql Server would be upgraded.