This applies only to Windows XP Service Pack 3 (SP3). To find out how to check your Windows version, click here.

From the Start menu, select Programs (or All Programs) and see if you can find Microsoft SQL Server 2005 (it should be a yellow folder, and may be toward the end of All Programs)

If you cannot find Microsoft SQL Server 2005, then the error you are experiencing is related to installing SQL Server 2005 Express on a system with Windows XP SP3.  This error was introduced with Service Pack 3 and there is no corresponding fix for the SQL Server 2005 installation from Microsoft. 

Following is a workaround:

1. Open the Windows Control Panel and select Add/Remove Programs
2. Remove all components that start with Microsoft SQL Server
3. Try to remove MSXML 6.0 SP2 (KB4954459).  This will probably fail.  If it removes OK, proceed to Step 9
4. Download and install the Microsoft cleanup utility at:
             http://www.horticopia.com/updates/msicuu2.exe
            If available, you can choose "Run" from the download menu instead of "Save".
5. From the Start menu, All Programs, run the Installer Clean-up Utility
6. Highlight the file MSXML 6.0 SP 2 and click on Remove button
7. Click on Exit
8. Reinstall the Microsoft SQL Server 2005 Express as described in http://horticopia.com/support/OnlineHelp/Version5SQL_ManualInstall.htm
9. If necessary, reinstall HORTICOPIA Professional.  When prompted for Update or New Install, choose Update