Books online refers about upgrading existing installation and in your case you can upgrade Personal edition to Standard edition: How to perform an edition upgrade within SQL Server 2000 (Setup)
To upgrade a SQL Server 2000 installation to a different edition of SQL Server 2000
Insert the Microsoft® SQL Server 2000™ compact disc for the edition you want to install into your CD-ROM drive. If the compact disc does not autorun, double-click Autorun.exe in the root directory of the compact disc.
Select SQL Server 2000 Components, select Install Database Server, and then setup prepares the SQL Server Installation Wizard. At the Welcome screen, click Next.
In Computer Name dialog box, select Local Computer or Remote computer.
In the Installation Selection dialog box, click Upgrade, Remove, or Add Components to an existing instance of SQL Server, and then click Next.
In the Instance Name dialog box, click Next.
In the Existing Installation dialog box, click Upgrade your existing installation, and then click Next.
If Setup detects that you are doing an edition upgrade, the Upgrade dialog box appears. Click Yes, Upgrade my <text specific to the upgrade> to upgrade the feature set of your current installation, and click Next.
After the upgrade is completed, you are prompted as to whether you want to install additional components. If you click Yes, the Select Components dialog box appears. Accept the defaults or select the additional components you want to install, and then click Next.
You can select an item in the Components list, and then select items from the related Sub-Components list. Click to select items you want to install; clear the check box of the items you do not want to install.
When you are finished specifying options, in the Start Copying Files dialog box, click Next.
In the Setup Complete dialog box, click Yes, I want to restart my computer now, and then click Finish to complete the edition upgrade.